A relay that runs on your phone. https://github.com/greenart7c3/Citrine
Discussion
Wouldnt that use a lot of bandwidth and resources for a small mobile device?
Relays don't use a lot of system resources. And the bandwidth is zero since it's local.
It would only be zero if you only use it like a cache. I think you can also use it as a personal relay and read/write/broadcast from it to your other relays. That wouldn't save you bandwidth (I don't think), but it would probably speed your client up a lot, make it easier to use multiple clients (only one relay to install) and would work as a backup.
Wouldn't it use less bandwidth, as a relay query is more efficient than a client one?