i m having a project in which we r deciding(its not part of original project) to provide security for our software through the hardware.. like we want that during the execution of the program, the program from time to time send a signal to the hardware device connected on com or paralled port and the device return a signal and than the main program continue execution... but the problem is that how to construct this hardware device.. wot it will need ? a processor and some sort of ROM.... and how we will program this ROM..?? is this whole setup implementable at home level and light on pockets.
Anyone experience who can guide to the right part..

Thanks