Basic Viper automatic start. Fob is slim enough for me next to the factory key that is. Bonus, it unlocks all the doors at one push, can pop the hatch, and if I feel the need to keep it running while I run into the variety store so the occupants can still enjoy heat or AC I can hit the start button, turn the ignition key back, lock the vehicle and take the key with me.
Vehicle won’t shut off either when you unlock and open the door like the OEM unit does (if you touch the brake pedal or open the door without using the fob again it will). Anyway, other units probably have these same optional features but the range on the Viper product is excellent too.