Software reviews: Sensors working overtime in mobile devices

Modern mobiles are full of sensors, with more uses than just the obvious ones. We look at a few apps that take advantage of them.

Sleep Cycle

The adaptive alarm clock

Alongside all the radios for Wi-Fi, Bluetooth, GPS and of course cellular communications, modern smartphones and tablets are chock-full of sensors - sensors for sound, light, movement, magnetism, even barometric pressure. Indeed, smartphones have played a big part in enabling the Internet of Things, because volume production for the phone market has dramatically reduced the cost and complexity of microsensors, which has in turn made practical propositions of all sorts of other devices.

And while those sensors have primary roles in navigation, gaming and the like, clever app developers keep finding new things to use them for. One that only seems obvious when you think about it is sleep monitoring - it does mean taking your mobile to bed with you, a habit many of us will have tried to break, but it can then use its sensors to track how we move in our sleep and use that to infer how deeply we are sleeping.

Why would you want to do this? Well, it’s only a short hop from tracking your sleep quality to using an adaptive alarm clock such as Sleep Cycle. Available for both iPhone and Android, this app aims to wake you when you are sleeping lightly and are therefore more amenable to it, rather than shocking you out of deep sleep and leaving you groggy. 

On the iPhone, it can track your sleep pattern either using its movement sensors or the microphone. The latter is to be recommended, not least because you just need to place the phone on your bedside table with the microphone facing you. One neat trick is that if there are two iPhone users sharing a bed, they can link phones over Wi-Fi - this enables them to more accurately detect where in bed a sound comes from. Beyond this it doesn’t need a connection, so you can put the phone in flight mode to avoid disturbances.

For now, the Android version of Sleep Cycle only uses the movement sensors, although its developers say they are adding audio. It therefore needs to be reasonably close to the sleeper - which should mean it won’t get confused by the presence of a partner. The app advises keeping the device plugged in and not putting it under heavy fabrics, although we found it worked okay when partly under the pillow.

The results were intriguing, showing fairly regular 90-100 minute shifts between deep and light sleep states, as predicted by the app’s developers, and also correctly showing periods awake. The app then calculates a sleep quality rating based on how much sleep you get and the amount you move.

Sleep Cycle is free to use for a month, then £29.99 a year. The full version adds extra bells and whistles too (not literally), such as backing up your sleep records online, playing soothing noise to help you get to sleep, and the ability to make notes on your daily activities, with the aim of correlating these to your sleep quality and your moods on waking, so you can see what helps or hinders when it comes to getting a good night’s shuteye.


Wi-Fi Analyzer

Free with ads on Android

One of the most useful things you can do with a phone is scan for Wi-Fi. Whether it is to look for connectivity or to find the channel with the least interference to put your own Wi-Fi on, it’s a great tool to have. We like Wi-Fi Analyzer for Android, but there are similar apps for other devices.

Wi-Fi Analyzer opens with a graphical view of the Wi-Fi networks your device can detect, with each shown as a hoop corresponding to its channel and signal strength. From the network view you can get an idea of how congested the standard channels are - that’s normally 1, 6 and 11 for the 2.4GHz 11b/g band - and whether it is worth selecting an alternative. For instance, in the UK we can also use channels 12 and 13, but most equipment won’t do so by default. With the right device, and bear in mind that not all mobile devices support it yet, you can also scan the 5GHz 11a/ac band, which is often much less congested.

Swipe right or left on Wi-Fi Analyzer and other views appear, for example showing the same information in a more tabular form, or signal strengths over time, or a dBm meter selectable by SSID. What a scanner app won’t do, beyond telling you which networks are open and which are encrypted, is help you break in to one of them. Most will not show interference either, even if it is on the same waveband and causing Wi-Fi reception problems. However, Wi-Fi Analyzer does also have an advisor screen which gives quality ratings for the channels available.


Dormi baby monitor

Free or from 99p on Android

Anyone with a spare phone and plenty of call time included in their tariff may already have thought of simply dialling it up and using it as a monitor - or a spy device. It would be much better though if you could use other connections too, and perhaps only open the connection when it is needed.

That is what the Dormi app does, being able to open a channel over whatever medium is available, although Wi-Fi is preferred for obvious reasons - Wi-Fi is also how you pair your devices, which must be done explicitly, for obvious reasons. Once paired though, you could for example connect the child device to a Wi-Fi hotspot running on the parent device, in case no local Wi-Fi network is available, or connect one device to Wi-Fi and the other to mobile data, and so on.

It then monitors in the background, beeping and turning on the video for a few seconds if noise is detected. You can even turn on the child device’s flashlight remotely, press a button to speak from it, and see its data usage and battery levels. Although the app is free, actual usage is only free up to four hours a month. Beyond that you can buy a monthly, annual or lifetime subscription.

Hamway Apps

Metal/EMF Meter

Free with ads or 99p on iPhone

Many mobile devices have a magnetic sensor to help the device sense direction, but it can also be used simply to detect magnetic fields. That is what apps such Metal/EMF Meter for iPhone do (EMF Detector for Android is similar).

What we mean by detecting EMF - electromagnetic fields - is debatable. This is in part because the EMF label has also been adopted by those interested in paranormal phenomena, many of whom believe that paranormal activity is accompanied by a jump in EMF activity. Others believe that EMF from high-voltage power lines may harm those living underneath. 

The fact is that many smartphones have magnetic field sensors, that a lot of electrical equipment generates magnetic fields, and this app can tell you how much the former is detecting of the latter. Why would you want to know? Partly it’s that the presence of steel and electrical cables has a small but detectable effect - an app like this can’t match a proper pipe and cable detector, but it’s a start.

Another part is curiosity, plus there are national and international limits for maximum safe exposure - remembering of course that the inverse-square law means that field strength falls off dramatically with distance. This is something the app shows very clearly as you bring it near an obviously magnetic object such as a loudspeaker or fridge magnet. Indeed, the value in an amusement such as Metal/EMF Meter may instead be in showing just how little EMF we are exposed to under normal circumstances.

Sun Light

2G 3G 4G LTE Network Monitor

Donations on Android

The most significant radios in your phone are probably the cellular ones that give you pretty much ubiquitous connectivity. But modern networks vary considerably in speed and capability, and they are patchy too.

It can be useful, then, to get a picture of what connectivity your phone is experiencing - how long it hangs on to a 4G LTE connection, say, versus languishing on slow but potentially longer-range 2G. This is where Sun Light’s Network Monitor comes in, keeping track not just of what connection your phone has, but also whether its 3G data connection is merely fast HSPA or even faster HSPA+, say. Your phone will normally tell you this, but only for the moment when you look at the signal bar. Network Monitor tracks it over time, for example telling you what percentage of your week’s connectivity was what. You can even set it to alert you when it loses the signal, or to show the current connection type explicitly in the status bar. The one caveat is that it gets confused by dual-SIM phones, or at least by having two active SIMs, and can’t tell what type of connection it has.

If you are getting consistently poor connections, one useful trick can be to use a foreign SIM in roaming mode instead of a local SIM. Most network operators will have multiple roaming agreements in each other country, with the phone latching on to the best local network it can find.

Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.

Recent articles