There is a fair chance one is already in the rig. Small white puck, little screen on the front, bought two summers ago to settle whether the back bedroom really got as cold as it felt, and living in the drawer with the tire gauge ever since.
That is the Govee H5075, and it is what I point people at when they want to try monitoring before committing to it. The same puck turns up in kitchens, greenhouses and gun safes, and there is nothing to configure. What makes it that painless is the way it talks.
Why there is nothing to pair
Bluetooth sensors come in two families. One kind keeps its readings behind a connection: you pair with it, a session opens, you ask it for a number. Only one device holds that connection at a time, so a sensor tied to your phone tends to go quiet the moment anything else tries to read it.
The H5075 sits in the other family. It broadcasts continuously, throwing its current reading out to anything in range whether or not a single device is listening. Nothing pairs to it and nothing claims it, so your phone can sit in the Govee app all week while our hub reads those same broadcasts from the other end of the rig, and neither one knows the other exists. Setup, in the end, is deciding where it goes.
The hub decodes those broadcasts today rather than intending to at some point, and the device page spells out what comes off it and where the caveats sit. Close relatives broadcast in nearly the same format, which is why the H5074, H5100, H5101, H5177 and H5179 are supported alongside it. If the puck in your drawer turns out to be something else, the compatibility database settles it before you go shopping.
Three readings, one sensor on your plan
Temperature, humidity and battery level come off every broadcast. Three numbers, one puck, and on a RoamVitals plan that puck counts as one sensor rather than three, because we count physical devices and a device is the thing you bought. Humidity is more useful than people expect, too, since a rig shut up for a couple of weeks will tell you about the damp before you can smell it.
Battery level is the reading everybody scrolls past and later wishes they had not. A flat sensor does not report a problem, it reports nothing, and nothing looks precisely like a rig where everything is fine, so you go on trusting a number you last saw in March. Set an alert on it now and that whole failure disappears.
Put it where the air is
Three places it should not go: an exterior wall, direct sun through a window, and anywhere sitting above a heat source. Each of those returns a perfectly accurate reading of something you did not ask about, the wall or the sun or the appliance, and it stays confidently wrong all afternoon while you read it from two states away.
Chest height in the living area, out of the sun and out of a shut cabinet, is the placement that means something. Freeze risk is a different question, because there the sensor wants to be near the plumbing rather than near the people, and the freeze protection guide works through where it goes.
Range reality check: Bluetooth is quoted at about 30 feet in open space, and an RV is a metal tube full of appliances, so the honest figure indoors is lower. A sensor at the back of a long rig dropping in and out is expected rather than faulty. What to do about it.
Where it stops being good enough
It is a consumer comfort sensor and not an instrument. That matters less than it sounds, because the decision you are making from a trailhead car park is whether the rig is at 96 degrees and climbing, and the H5075 is comfortably accurate enough to answer it. It is the wrong sensor if the reading itself has to hold up to scrutiny.
When accuracy does matter more than price, the RuuviTag is the honest recommendation: an open published protocol, a sealed enclosure, and it holds calibration in a way the cheap sensors do not. It costs several times as much, and for finding out whether the dog is comfortable and the pipes are above freezing, that is money you do not need to spend.
So go and dig the drawer out. Fresh batteries, chest height, out of the sun, an alert on the battery level, and the cheapest useful thing you can add to the rig this weekend is one you paid for two summers ago.
