So far, all old analog cell phones I have picked up dial 911 without paid service. I call the local dispatcher on them to test this, no problem, so a larger bag phone, generally free and incredibly easy to work on due to their size, could work, a controller made from something like a basic stamp or pic chip could dial for you, send 911, *911 etc to get a connection. Another way is to set your dialer, if possible, to allow outbound 911 only and reject all other call requests. If you go with an analog phone (AMPS), contact your local PD about testing if the service still exists with carriers around you, maybe during off hours.
Kurt
