Timer yes, i have seen one in the Bots Hacks section, but it arent able to kick players cause its not bound to the client.
Either you get a trusted taxi manager, you let him get free Taxi, and everyone pays him while you are afk and collect later on all the gold from him (not easy to find a trustful person i know :) )
Or you do other things and set a alarm, so you open the client and kick that guy if his time is over..