Recently, Rob Mitchell of Paperclip Robot asked me to try out a new product called BubCap. It's a sticker you place onto your iPhone, iPod, or iPad that covers the Home Button, making it harder to click. It's available three levels of rigidify and does its job well.
Why would you want to do this? There are several compelling use-cases. For example, Paperclip Robot sells many BupCaps to parents who want prevent toddlers from exiting a certain app and wandering over to Daddy's e-mail account or Mommy's home finance program. The covering material is stiff enough to limit toddler access without hindering adult use.
This isn't a solution for unmanned installations -- you'd want to use a more permanent, lockable device as a thef