I saw a couple YouTube videos last night about setting up a repeater using a pair of cheap hand-held radios and, at its simplest, an audio patch cable to connect the speaker output of one radio to the mic input on the other. Set frequencies correctly, turn VOX on, and what one HT receives will be retransmitted by the other -- potentially even cross-repeating between 2m and 70cm bands, or whatever bands your radios can use.
There are potential issues with doing this on a non-emergency basis -- protecting the radios from weather, keeping their batteries charged, preventing someone from finding the setup and saying "Hey, free radios!" The one I'm concerned with at the moment, however, is FCC legality. It's my understanding that periodic ID, at least when active, is legally required, but none of the other repeaters I've listened to seem to do this.
Since the cheap HT sets don't have this capability, I'm concerned about the legality of operating a repeater that doesn't identify itself. Just because another repeater doesn't (that I've heard), doesn't mean it's legal to do things that way.
Is there an inexpensive way to insert an ID generator between the receive and transmit HT units in this kind of setup? It would need to detect activity, wait some period of time, and then send an ID, as well as sending periodically if there's no activity. Either voice or Morse is legal, but presuming this will be a digital playback system of some kind, either one is easy to set up.