Okay this is weird item Im selling on the store. I've recommended the ScanGauge 2 (which is on the store too) but the price is pretty hefty for a Trans Temp Gauge. So I have one of these wifi OBDII readers that I have used for almost eight years now. You use the OBD II Reader and the app Car Scanner ELM ODB2 (iPhone or Droid), purchase for $7 (lifetime) and load up ATF Var 1.
Works withOUT Cell Service. Connects via WiFi.
BOOM - you have a Trans Temp Gauge on your phone or tablet!