1) Transmitting power and data through the case. Current pcb rev will have micro USB for power and a simple debug header but need power and IO routed for docking station.
2) FPGA power draw. The T20 FPGA is very cheap and low power for ram based but it still may be too much for a watch. An Igloo2 based device may be a better path
3)Supported peripherals: Pulse, manometer (compass), microphone, speaker