Thanks to those of you who have responded and DM'd with suggestions. I ended up pulling the trigger on a pair of devices - a remote sensor with waterproof probe and a Wifi gateway to get the data over Wifi rather than Bluetooth (not enough range). Both pieces for about $80 total. I don't have high hopes for the app that pairs with these devices, but I'll give it a try.
The reason I really want a separate external temperature probe is so I can measure the actual temperature of a liquid in the space, not just the air temperature. I suspect the temperature swings in the bottle are a lot less severe than the ambient temp changes, and I'd like to get confirmation of that.
If these devices don't really give me the data I'm looking for, I'll likely just grab one of the Govee sensors a couple of you have recommended - they seem inexpensive and simple.
Edit: GIVEAWAY WINNER🎉
The giveaway has ended. Thank you everyone who entered. Congratulations to winners u/rottenpupil to win the IBS-M1 Wi-Fi gateway & IBS-TH1 Smart Sensor! Please PM me to redeem your prize.
Here are 15% off discount code for the these units if you're still interested:
IBS-M1: LEKCLFVM
IBS-TH1: NEHRSNHL
Canadian store: IBS-M1: XUDLMCWY
Canadian store IBS-TH1: 4IOKR5YJ
See you guys on next time giveaway!