It is fairly common practice for someone accused of a crime for the first time to be Released on their Own Recognizance (ROR) without bail. I could easily see a system where you are outfitted with an ankle monitor with GPS and a radio beacon similar to house arrest but only activated after either 1) Failure to appear or 2) Detection of tampering with the ankle monitor.
Currently yes. They actually require a land line to be connected to the base, but the technology exists and can be adapted to use mobile networks instead.