Mobile Device SSH Keys

Anyone have any pointers on what the "best practices" are concerning SSH keys on mobile devices? It's just me and it's just a personal device—a Nokia N800. The concern is over key passphrases in an environment that doesn't provide (by default) askpass/agent infrastructure, thus making them tedious at best. Should I:

• Come up with (find/package/develop) some kind of ssh-agent/askpass for the device? It wouldn't be hard but I would rather not.
• Disable the passphrase on the key?
• If I disable the passphrase on the key, generate a secondary key for exclusive use on the device?

I guess my concern about no passphrase is if the device gets stolen, how easy would it be to revoke the key and how quickly I would be able to do that. Obviously it would depend on the exact situation which you can't predict, but what are the practices of various other mobile SSH systems out there?