Was considering the Suunto D9 with transmitter but after some advise from the shop, i decided to settle for a D4. The thing is, the price is almost double for a transmitter and no matter how reliable the computer is, I am more comfortable with analog gauges. For me, even if I have that transmitter, I would still want my conventional analog gauges for peace of mind, they willl most unlikely fail you. So personally, this is a very nice to have gadget, if you have the extra $$$. Not sure about inteference or accurate reading.