I still have the modules around here somewhere!
No native serial ports, though, and the restriction of things needing to be on the same circuit kind of puts a damper on things. In my college dorms everything in my room was on the same circuit.
re: the serial ports - If I remember correctly the signaling to the module was done on handshake pings (because serial data could "pass thru" the module). They'd probably be pretty easy to bit-bang from any 5V logic source.
As a high school student I helped my school do some sys admin stuff, and one day I was stuck in a server(?) room while the guy who had keys etc. was away in another room and floor. So I ssh-ed into the machine he was likely working on and ejected the CD ROM back and forth until I caught his attention :D
Her sister caught on but couldn't prove it.
The light was controlled by an X10 "firecracker" module. Neat stuff, for the time.
Anyway, she would do that to get my attention if I wasn't by the PC and she wanted to chat via ICQ.