Doug:

Only the more advanced home automation controllers have the ability to detect and avoid signal collision (e.g, JDS Stargate/Timecommander, Homevision, etc.) Some other lower end home automation controllers can be set up to send the X-10 signal multiple times which might help depending upon the application.

None of the RF or IR transceivers available will detect and avoid signal collision unfortunately. Regarding motion sensors, if you can run wires and have a HA controller (like the ones mentioned above)with digital inputs, you won't have the problem of signal collision.

Robert
RCI Automation