Ask HN: Review my ETA app

I made an iOS app that lets you let someone know when you'll arrive somewhere. I'm looking for feedback on whether or not it's useful, what features you think would be neat to add to it, etc.

It's in the app store (free download):

http://itunes.apple.com/us/app/crangle/id415138982?mt=8&ls=1

Source code available at github:

http://samlevine.github.com/crangle/

Thanks for your time everybody.