Keyless/remoteless entry system
So my car (1996 Saab) is setup with push button start (with two switches controlling the ignition and accessory circuits), this allows me completely keyless use of the vehicle once I gain access to the interior of the vehicle.
So I have just been carrying around my remote to unlock (and disarm the OEM immobilizer), but since I don't have to remove my keychain to start the car, it's often a pain to fumble around for it just to get in the car.
I was thinking about doing a cellphone based system probably via BT, but then unless I can get it setup where it does it automatically when approaching the car (not that easy since by OEM system shares the same button for lock and unlock and I'm not sure of an aftermarket system that would interface with Saab electronics) or I would still end fumbling around for my phone if I did it via an app.
Anyway during my research I came across suggestion of having a hidden capacitive touch button, I like that idea for:
1. I wont have to fumble for a remote, phone, etc
2. I wont need to bring my phone if I just run out to the car to grab something (would be a pain if it was charging or being used, etc)
3. Nothing to lose or worry about going dead, etc
Upon further research I also found some capacitive touch grid sensors that can recognize 'something unique' (I assume like pattern unlock on a cell phone). I was thinking that for the added security, I would pair Arduino control board that would momentary close a switch (that is wired in parallel to the lock & arm/unlock button on a spare OEM remote inside the vehicle, this way I can arm/disarm the OEM immobilizer).
Anyway has anyone done this before? How hard is it going to achieve a input from a touch sensor to the Arduino and have the Arduino momentary close a circuit between points (tho I suppose I could use a relay so as long as I had it output a momentary high voltage that would suffice).
I have found standalone capacitive touch buttons (with a momentary function) for about $25, should I just use one of those and with the fact that it's hidden and no one would suspect looking for it to be enough security.