If you're a busy person, it can be hard to remember to put aside the time to relax. Even usually relaxing activities like watching bilge on TV or taking a bath can be overtaken by email checking. Let's face it, useful as it may be, the iPhone makes this situation a lot worse. SleepStream redresses the balance, letting you make your iPhone a core part of your unwinding routine.

Based solely on sound, you'll need headphones for the app to have any effect, but we were surprised at quite how effective it was.

It creates a soundscape made up of two core components. The first, and most important, is the stereo drone. There are five different settings for the drone, ranging from ‘energize' to ‘sleep', depending on what effect you want SleepStream to have. The more relaxing you want the app to be, the close the tone will be in pitch in each of your ears.

In ‘Sleep', the two channels match, but in ‘Energize' there's a pretty hefty tonal gap between what's piped to your two ears. This is the scientific component to the sound the app produces, and probably the element we found the most effective.

Surrender to SleepStream and you'll find it altering your natural breathing pattern as these tones cause a internal reaction that signals certain sleep-like signals to your brain. Apparently. To start with though, the tones are quite uncomfortable to listen to.

The other half of the sound SleepStream produces is designed to ease you into the effect of the underlying tones, although they come with their own relaxing properties too. It's made up of one of a whopping 34 mostly recognisable, mostly real-world sounds that add texture to the tones. They range from obvious choices like a crackling fireplace and falling rain to a lounge-style piano piece, and further on down the line to some surprisingly dark-sounding drones like ‘Dark Chimes‘ and ‘Oceanic 815‘.

Unfortunately, some of these samples are a little too short for their own good, with clear looping points. The repetition does end up a further relaxing element, but when classic relaxing sounds like rainfall and cricket noise devolve so quickly into a clear loop that's mere seconds long, we can't help but be a little disappointed. However, all of the sounds are of a high quality.

There is a mode that loops between the 30+ samples, but we found that there's an audible clicking whenever a new sample enters, making it of little use when it diminishes the sound's relaxation effect. You can however change the balance between the two halves of the sound using a slider- so you can have just the tones or a looping sample playing if you wish. There's also a timer mode for those that want to use SleepStream Plus as a sleep aid, which stops the sound after 20 or 60 minutes.

We found it more useful as a calming influence when in a bustling environment, such as on public transport, where it proved to be genuinely soothing. It functions surprisingly well, although we'd love to try out a version where some longer form samples feature.