I have three of the HomeSeer motion sensors that @erktrek mentioned and they have been working quite well outside for a number of years now. Just replaced the original motion sensors that were attached to the exterior security lights.
The "only" gotcha is that you have to leave the circuit on. So the light switch we have for those security lights just stays on and the motion sensors control the lights directly (they also have a light sensor so you can make sure they are not coming on if it is already light enough out). Plus all the notifications come back quickly and I have a rule set up to have them trigger other lights (such as the one by the front door) depending on what goes by.
