Good progress on my build today. Everything seems to be working with ubidots, I've got that feeding triggers into IFTTT to turn a warming pad on/off (powered by a smart plug) via webhooks based on high/low temp events. I needed to add a single 5g sugru pack to the base of the cylinder for ballast and to secure the pcb, and then pushed a spare button and screw into that to get 25deg float in water by trial and error (reading 25.2deg in 25C tap water - good enough for me!).
Just need to calibrate in a sugar solution, then try an actual brew!
Most people seem to focus on the gravity readings with ispendel... But I'm most looking forward to being able to monitor and control fermentation temperator through winter in my garage!
I'm planning on putting a guide together on this at some point, in case others are interested.