I have a couple (either 2 or three, i can't remember) from amazon that were under $100. Both have built in batteries, and one is designed to be charged and then

I have a couple (either 2 or three, i can't remember) from amazon that were under $100. Both have built in batteries, and one is designed to be charged and then placed in a greenhouse while you're working in it, another is designed to reference between two "rooms" or whatever. None of them log to sd card. I'd fully expect a functional solution that does logging with all of the other features to cost more than $100, but if i can be proven wrong, i'd buy one, for sure. For example, with an SD card we now also need a clock - which ideally would have a different power supply than the sensor suite, otherwise the timestamps will overwrite if the supply is lost, or otherwise be incorrect.