I'm intending eventually to play with these MaxBotics sensors in a room entry / exit count configuration. I already have a PIC processor attached to them (Gerry Dupreys) that reduces the serial chat to just the info you're interested in and can just give logic I/O as well.

Fortunately the majority of my doorways are thick - walls are 2-3 feet width and I intend to place the sensor at the far extreme facing towards the room but diagonally across the doorway. The PIC will remove all distance reports outside a preset range and so I should be able to eliminate any within room movement. Then with a bit of code adaption I should get a trigger plus 'near to far' or 'far to near' report from the sensor which would indicate if someone was entering or leaving the room.

It remains to be seen how well this will work in practice but it could tie in well with the new Cortex directional entry/exit support in V24.

My slight reticence is any audability of the ultrasonics by my dog - need to do a bit of research here to see if it's going to be an issue.