According to the current Cateye web site, there is no model CC-RD420DW. Apparently this was the Strada Digital Wireless. It is no longer available. There is a Strada Wireless CC-RD310W-U, but it does not include cadence. It looks like the successor is the Padrone Digital CC-PA400B. That is the one I was looking at. I have sent an inquiry to Cateye about pairing 2 computers to 1 sensor but haven't received a response yet. I sent a similar inquiry to Wahoo about their bike computers, and was informed that they can only pair 1 to 1: a sensor can be paired only to one device at a time. It appears that the actual experience of folks is that it is possible to pair 2 computers to 1 sensor, so I guess I'll buy two computers and try it out. If it works, great.