You can imagine the problem this causes, since every time I start an app for her she exits out of it as soon as she gets the urge to press that tempting little button. Anywhere from two seconds to one minute after I've handed her the phone to watch Sesame Street she is holding it out begging for me to fix it. I re-start the app, hand it back, and the process repeats.
I searched and searched online for a way to lock the button, but found no solutions, since Apple doesn't let any apps disable the function of any of the hardware on the phone. Then one day I discovered the solution: Bub Caps.
Applied like a screen protector for the home button, Bub Caps create a semi-rigid surface over the iPhone's home button to help keep toddlers curious fingers from constantly closing out of applications.
Bub caps are made in differing degrees of strength, so for older kids and ipads you can get harder plastic. They are removable, and don't leave anything sticky on your phone.
They come in packs of four for $5. You can get them at bubcap.com or amazon.