Galvanic coupling has been shown to be the best method for low-power on-body data transmission. This approach has been extended toward wireless communication between implanted devices, building a real intrabody sensor network. To show the feasibility, a test system has been developed and implemented. The measurements are compared with the 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 medical long-term surveillance of patients. To achieve this goal, small circuit size, low power consumption, and electrical safety have to carefully be considered.