Interestingly classed as a 'game' rather than an 'app', this is from the description in the Windows Phone Store:
It's time for bed and you've run out of ideas for soothing your kids and lulling them to bed? Try playing 'Sleeping Child" Application on your mobile phone and you'll be surprised to see your children doze off in a few minutes! Best lullaby music, sweet and animation picture for your "baby sleep"!
Download this great combination of relaxing sounds for children and have a good night. Please consider to post a review for application if you feel happy.
The idea is that you mount your Windows Phone on the side of your todder's cot or bed and leave the app to it. They'll watch the screen, listen to the music and Zzzzzz...... Hopefully.
Here's Sleeping Child in action: (Or should that be 'inaction', etc?)
The starting screen, hit Start to just get playing, or 'Advance' to set up....
Half a dozen frames/scenes, each with individual animated touches, all interesting enough to watch for a minute and boring enough for a child to fall asleep to....
Setting a timer ensures the music and display stop after a while, possible a good battery saving feature for your phone, at least....
Setting a playlist from the supplied tune compilations....
Each scene and tune combination is then part-rendered, taking about four seconds and then playback starts....
In this case there are bubbles, and wiggling bits, plus fish that occasionally swim past....
Ahhh.... starting to rain on the little frogs..... The artwork here is original and well done, if I was two years old I think I'd love it all...
All of this sounds idyllic, but there are some caveats. One is that the music tracks change somewhat abruptly - the developer might like to fade them into each other better.
The second is that although the main display is 'touch-proofed', to stop anything happening when the toddler touches it, the Windows Phone control buttons aren't. In use, I'd suggest that the mounting cradle (in cardboard or some soft material) be arranged to cover up the Windows control keys, lest the toddler press something they shouldn't and be staring at a Windows Phone application screen. Or kicking off a game of illicit Angry Birds....
It's easy to point out that Sleeping Child's animations and soundtrack are somewhat boring - but that's exactly the point. They're designed to put the toddler to sleep and not to excite them in any way. Definitely worth a try. You can buy Sleeping Child in the Store for £1 or so here.