DX 433Mhz Wireless Door Contact 248919
From SifWiki
This is based on a EV1527 encoder so should work with RCSwitch.
Device is a pretty simple reed switch with a magnet, normally closed and triggered when the connection is broken, this should be easy to hack to other usage.
Affiliate link to DealExtreme: http://dx.com/p/248919?Utm_rid=65939668&Utm_source=affiliate