Car key lock status idea

I’m always worrying whether i’ve locked the car using the remote electronic key crap.  I’ve had to walk back many times to the car after parking to check if I’ve remembered to lock it.  I was thinking why not have an indicator on the key itself which says whether the car is locked or not.  Well I’m pretty sure someone’s thought of this earlier, but why don’t we have something like that ? I badly need a key like that for in fact anything that needs to be locked. The constant worrying about whether I’ve locked something is starting to annoy the crap out of me.  How fucking hard can it be, lock and key industry ?