For this inquiry of yours, actually, regarding the usage of sensors with our device, there are a lot of analog temperature sensors in the market but it will not show you the temperature value directly. You will be getting voltage levels and you need to convert these voltages to temperature depending on the sensor you are using. But it seems you are already using the analog input of RUT955 to monitor the battery voltage value of your Camper Van. In this case, it leaves you using a temperature sensor that is working on TCP/IP let's say this sensor because the Digital input will only read logic high or logic low.
But we cannot suggest any exact temperature sensor for this use case scenario you are having. So, I hope this gives you an idea.