I was working on a robotics thing with my plug and blew out most of the motor control system so my robotics plug project took a major turn toward the back burner for a while.
But, recently i had the "pleasure" of helping a company relocate offices and got chatting to their security guys. Anyways, long story short I did a bit of searching round the web and there are plenty of components for building a security system that should be plug-compatible. By all this I mean proximity card and motion detection stuff. Alot of the components security people use are actually hooked up with serial (rs232/485/ttl and the like) and are very simplistic (they get the job done, basically) and not alot of them have much in the way of real networking capabilities.
There are quite a few rfid card readers (door entry systems) out there that talk either serial or usb (and are usb-to-serial anyways), same goes with motion detection systems and door opening mechanisms. Ultimately you could pull the plug out of its case, throw it into another case with a 12v SLA battery backup and the power requirements for driving it all are surprisingly low. Theres not alot of software out there at the moment for running on linux to control such a system, but it really wouldn't be overly complex to write something web-based to do all the work. Theres the possibility of adding something like zoneminder on there too at some point too.
The problem I cant solve though is that in order to do all this, even a small system is clocking up about 8 serial connections and I cant find anything that would allow me to achieve that number of serial connections (without just plugging in multiple usb hubs and usb-to-serial adapters - im not sure the plug would even survive that many connectors anyway). There are a couple of multi-serial-port usb adapters out there, but I was curious if anyones seem anything that allows some flexibility (as in one usb port and scale up to 30-odd serial connections)?