A timer is nice to have if you are in a hurry and don't have time to wait for the turbo to cool (anyone else ever had to boost all the way to work or school?). I wouldn't buy just a timer, I would get something that has a few other features. The one I have for sale has a thermometer, volt-meter, several "stopwatches", and one or two other things that I've forgotten. It can be set to monitor the ignition and increase/decrease the idle time accordingly.
