I'm not looking for ways to prove the bicycle is mine. I can photograph it, record the serial number, show my receipt, etc.

What I want is to get the bike to find me after it's been stolen. (Almost) every bicycle has a serial number, but nobody actually checks it against registries to see if the bike is stolen. And which one(s) to check?

Having a URL on the bike is idiot proof. Anybody who sees it can type it into a browser and will (in a single, easy to take step) get back the page saying "STOLEN". Then (assuming there are decent people out there) they'll contact me with info on how to get it back.

So, the only problem is: How do I affix/stick/paint/whatever the URL onto the bicycle so that it will survive until said-decent person comes along?

Engraving sounds like a good solution. For steel I'll need to do something after to make sure it doesn't rust. What would be the best thing to do to a steel frame (or an aluminum frame) after doing such engraving? Would I even need to do anything for aluminum? The thing that worries me about this one is that if I do it too small, the thief can just stick a sticker over it. I think whatever I do, I need to make it big, like over the whole length of a top tube or down tube.

thanks