Galvanic coupling, which has been shown to be an excellent method for low-power on-body data transmission, is extended toward wireless communication between implanted devices, building an intrabody sensor network. A test system was been developed and implemented, and the measurements compared with numerical simulations. The prototype offers four concurrent channels with a throughput of 4.8 kb/s. The main focus is the future implantability of such a miniaturized system for the long-term medical surveillance of patients.