I am keen to get an alarm and a turbo timer. Are the ones that are 2 in one any good? I hear that they have remote start too. That would be great "wank factor".
One of the main advantages is that you can use your turbo timer, set the alarm and walk away.
A lot of alarms don't cope well with being switched on when the engine is still running, which means you need to sit and wait for it to cool down or leave your car insecure.