Volts welcome to the forum. Electircity has been a topic for discusion arround here for a while. You might want to check out the thread on it. Also a search on electricity might bring up some good ideas.

As far as home built electrical devices goes IMHO, as an electrical engineer, they pose great safety risks. You might want to investigate the comercial tens units. Some even have a computer interface.

Play often but always play safe.