This is what has been needed; now, instead of a voluntary app, it needs to be hardwired in. Sorry, libertarians -- cell phone activity in the driver's seat has been pretty conclusively shown to be a hazard to many people's health. It's WORSE than DWI!
There's a guy on another site I frequent, who asserts that people of different skills should have different freedoms; of course, he feels he can handle TWD. As he is a frequent cyclist (his own admission), I find it a bit disconcerting that he would promote this idea. He has never explained to me how anyone is going to figure out the comparative skill levels of 190 million people, or how he can justify easing off some people who show poor habits but have not yet hurt/killed anyone.
Yes, a lower-powered GPS feature would be advisable; I also kinda like the idea that a timed puzzle could unlock the phone, for times when you're a passenger (although a passenger could do this for the driver and defeat the whole thing).
Bottom line, though, I'd choose IZUP. Wean these overgrown babies off the wireless teat.