Just got one of these and am happy so far. Documentation is poor, but there are some helpful videos on Youtube. Problem is they're all aimed at iPhone users, which seems like the primary market for the device/software.

On Android, I don't see how to get the "Temperature" reading working - I can add the temperature data cell to a custom screen, but no actual temperature reading appears.

Update: Ok, it's not the RFLKT that's the problem, as it's just a dumb head unit for the phone, displaying whatever data the phone has for it. The problem is the Wahoo Fitness app does not have a temperature reading on the page where the cell for it is defined, i.e. the "altitude" page. So my question has the wrong subject - it should be, "Where does the Fitness app get the temperature from on an Android phone?"

I thought that only the RFLKT+ had the temp sensor, and of course has been discontinued.

If it's anything like the iPhone version, the answer is "you can't." You can use another app like Cyclometer to get additional data (altitude, grade, temp).

The more I look into this, the more I think neither the RFLKT or the Fitness app is the problem. I'm using a Samsung Galaxy S5 Active, and googling produces some "authoritative" comments saying that the S5 actually discontinued the temperature sensor that was present in previous generations of the phone. You can also find posts saying the opposite, but it makes sense to me that the Fitness app might be querying a sensor that, on my phone, is just not there.

The RFLKT does not have a built in thermometer, as does the discontinued RFLKT+. It has to get that information from the phone app which will either get it from a thermometer built into the phone or quarry a web service to get the temperature in your location. If your app uses a web service to obtain weather information, it will use your cellular service in order to do so. I have a RFLKT+ that I've had for a few years. The thermometer on it isn't that accurate and is usually way off more than it is close to being correct.