This sounds good but how do you receive the voice message? Is it played automatically or do you get an alert and then have to open the app and play it back? Endomondo offers something similar when I am out training so the wife can send me messages (like "stop at the shop on the way home and grab the milk"). The advantage is that it plays the message without me having to do anything so the phone can remain in my pocket. but if I don't hear it properly I can "play it again".
This sounds like it could be really handy but I'd want to know how it plays back messages.