I think it's a great idea! It definitely has issues, but keep at it because it's a great start. Here's another feature idea: when I'm using xcode, i don't want other distraction to come in; so maybe find a way to make it harder for me to open browsers and other distraction (i see you, hn & reddit).
I agree with rodly that this feels like a different app. If someone does make it, I hope s/he calls it "No Touching!" after the recurring joke in Arrested Development, where every time a family member tries to touch imprisoned George Bluth, Senior, a prison guard yells "No Touching!"
