Users of Weatherlink Live uploading to Weatherlink.com will now see that under the wrench/spanner menu there is now a Health Data menu option, which provides info for details like battery status, packet reception, RSSI (transmitter signal strength) etc. This is also available for all Enviromonitor systems, though I doubt that there are many EM users regularly tuning in here.
I don't know, but would not necessarily expect this information to be extended to older upload devices in the future.
Also, I haven't looked at the v2 API documentation yet today but if it's not there already then maybe this health info will be available via the API too in the near future.