First, I have three good candidates for the beta test. It will be hard to choose among them, so I am afraid I don't need anyone else offering to help. Sorry...
The XTBr will still do direct X10 Boost like the present unit, but it will also offer the ability to repeat any X10 commands received on its own phase. Due to the size constraint, it will not have a digital port for TW523 emulation, and it won't have quite as much output power as its bigger brother.
Basically, it is intended to go between your CM15A and the wall socket like the present unit, but it will also boost commands sent by X10 transmitters located remotely. With X10 devices on both phases, a good tuned-circuit passive coupler must be installed near the distribution panel. And, because X10 signals quickly lose their strength as they propagate away from the transmitter, best performance will be obtained when the XTBr is relatively close to the distribution panel.
Even if the beta test goes well, this unit is still months away. It depends on how much time I have available for this project. Unfortunately, most of the next month must be dedicated to the IRS.
Jeff