we tried it a few weeks ago, it dunt work.
The CB has to be in range of a "receiving station" for the app, of which there are few in the uk, the lag is also supposed to be terrible.
S3s are awesome! Best phone ive owned. Had the S3 for a while spent pretty much everything on my new Landy. Though a night off from the pub will buy me a CB.
Tried to app today, as you said, it sucks and doesnt work.
Sorry to disappoint, but the CB messages on your phone actually stands for Cell Broadcast, not Citizens Band.
Bit of a useless setting tbh, never found a use for them.