Not sure if anyone remembers the old X10 PR511 floodlights, but it looks like there is finally a similar product on the market, using the INSTEON protocol. Those PR511's were the only 'automated' floodlights with motion sensor on the market until now. The new SmartHome INSTEON Motion Sensor Floodlight supports both INSTEON, X10 or both.
I personally had the PR511 installed for years, and while the idea was great, I ran into many reliability issues. The INSTEON motion sensor floodlight fixture can now be pre-ordered from SmartHome.com for $64.99 and are expected in stock by June 30, 2009.

I personally had the PR511 installed for years, and while the idea was great, I ran into many reliability issues. The INSTEON motion sensor floodlight fixture can now be pre-ordered from SmartHome.com for $64.99 and are expected in stock by June 30, 2009.