I built an iPhone app called Commit that tackles this very problem. It is in the review process right now and should be released in the next couple of days.
You can read a bit about it here: http://nathanbarry.com/a-little-bit-each-day/
You can read a bit about it here: http://nathanbarry.com/a-little-bit-each-day/
I run http://weekplan.net which is in a similar space and many people ask me for an iPhone/Android app. I have made a mobile stylesheet but a native app would definitely be a Win/Win/Win (iPhone developer / Users / Me)