We sell the Freewire line, and the products are 95% X10 compatible, the 5% being the previously mentioned RF frequency differences. I have personally installed the motion detectors (FWMD), they do require the messenger hub (FWMH) but work perfectly with X10 from that point. I have customers using them to trip home automation software as well as standard X10 modules with no problem. I also personally have the outdoor lamp modules (FWLROD) running Christmas lights with no difficulties.
We do have a sale currently for the 5 piece kit, I dont know the boards regulations on posting links and/or sales which would be considering "advertising" so if the admins allow I would be more then happy to post it.
Minor threadjacking, I would also like to offer a discount to all forum members making purchases by using a coupon code, however I still am wary without admin permission to do so.