Mycelium lets you create transactions while it is offline, and broadcasts them when it gets an internet connection. So it could still work with really spotty connections, just not instantly.
This feature is great! For example, i can't even open blockchain.info's wallet if internet connection is down. I can't even show someone else my public address QR code!
@Rassah: is there any time estimate possible for iOS development catching up with android development? At the moment a lot of features (even basic ones like PIN) are missing.