How to extend I/O Bridge wirelessly without additional microcontrollers.
Since the 204 has 4 digital inputs/outputs then adding wireless digital I/O is the matter of connecting to a RF engine. Since most RF engines use 3.3VDC, for low power consumption, then by obtaining a level converter is all that is necessary to connect between the 204 and the RF engine. Sparkfun has one for 2 in and 2 out that converts from/to 3.3VDC to 5 VDC needed by the 204.
In choosing the right RF engine, we look at many, but the one that was the easiest to use, with a built-in microcontroller, was the Synapse RFET. By loading a python script, into these RF engines you could create a battery operated Zigbee network of peers which would last for years on battery power. Typical applications would be a mailbox monitor/counter, garage door open/close status/counter, flood/water warning sensor, security sensors, garage door open/close activator just to name a few.
We bought a Zigbee development kit from Synapse / Digikey for a 2 node network.
The protoboard SN171 provided the perfect bridge to the Bridge 204 I/O electronics via level converters. Additional nodes or peers can be purchased separately.
If anyone is interested, we can point you in the right direction but you need some
basic programming and electronics knowledge and some extra money to spend.
Links:
Kit EK2100 -
http://www.synapse-wireless.com/ Level Converter -
http://www.sparkfun.com/commerce/product_info.php?products_id=8745 
