What is the oldest model iPod Touch to support Airplay in browser I want to use an iPod touch as a common interface for the office music - streamed through Grooveshark in Safari.

The iPod will be glued to a post in the center of the office, so I'm looking for the cheapest option. 

What is the oldest generation that supports Airplay from a browser?
The 5th generation iPod touch is the oldest device that is capable of AirPlay Mirroring.

The 4th generation can be jailbroken and can have AirPlay Mirroring enabled, but the hardware will mean that it may be laggy.