The most unique feature is the capability to mix and match these sounds to find a sound which matches your most relaxed state.
Sleep Sounds is also a universal app. Buy it once for your iPhone and iPad. You can use it on both your devices at full resolution.
The full version contains 16 sounds: Bird Song, Bonfire, Cat Purring, Cow Pasture, Creek, Distant Lawnmower, Highway, Horse Drawn Carriage, Light Rain, Night Crickets, Ocean Waves, Pendulum Clock, Thunderstorm, Tropical Rainforest, Whale Song and Windchimes.
The lite version contains 4 sounds: Bird Song, Bonfire, Creek and Light Rain.
Sleep Sounds is a universal binary that will work on your iPhone, iPad and iPod Touch at full resolution with a single license.