I was the victim of paying fine for loosing the keys in the ground so I have come up with this idea.
How many of us are searching the keys. House key, car key, etc. etc.. Yes, we know there may be a time you will be the key of your appliances. But the Solution for the current problem is, Just use the small mobile phone as a key-tag. You can afford to buy 10USD phone ok 20USD phone .