AirPlay can now be added to any first generation AppleTV by installing the Remote HD plugin and activating it using Remote HD iOS application.
Once the plugin is activated, any AirPlay enabled application can be used to stream video and photos to the AppleTV.

Remote HD's AirPlay supports:
- Video streaming from YouTube iOS app
- Movies and Podcasts from iPod iOS app
- Photo streaming from Photos iOS app
- Video streaming from iTunes 10.1 running on Mac or PC

Remote HD What is Remote HD?