A user connects to my web application,
I grab some sort of device ID through W3C standard protocols,
The user logs in,
I can then identify this specific unique device owned by the user (not just "iPad" - I'm looking for "iPad3_2C38TY43058" or even just "John's iPad").
This would let me design my web application to treat logins from this device in a specific way, know which of John's 5 devices he's logged in from, etc.
Is there such a protocol? Is there any method of identify a specific device as described?