Polar officially announced release of the RS800CX with multi-sensor compatibility, integration with Google Earth and ability to combine data files from multiple types of sports. As previously discussed on this blog (after the leak of few support articles on Polar site) the watch comes in several configurations RS800CX (just the watch), RS800CX BIKE (with W.I.N.D. speed sensor), RS800CX MULTI (with GPS G3 sensor) and RS800CX RUN (with the S3 stride sensor).
If you already own a W.I.N.D. sensor (except the power) you should be able to pair it with the watch and use just as you did with either CS600 or RS800 (looks like this one is replaced with the CX models, Polar still lists RS800G3 but I wonder how many people will actually buy it now that the RS800CX MULTI is released). If you want to take part in the newly launched challenges on PolarPersonalTrainer.com you will need to start loading your data also to the website as described in this support article. I tried just entering the data on-line, but Polar accepts only data from the HR monitor for the challenges. You can still log data manually, but they do not count against the challenges. If you swim with the RS800 line of HRMs (RS800/RS800sd/RS800G3/RS800CX) you will not be receiving HR data from the belt under water - the W.I.N.D. technology does not transmit under water (this is the same with T6c from Suunto and all Garmin HRMs that use the ANT+ technology for transmitting data).