All the vibrating alarm clocks I could find do not sync with your phone, and have to be set manually. I thought about getting an Arduino, but then I will have to build the whole thing by myself. The only logical conclusion I could come up with is to get a programable vibrator. But most of them are either very expensive of look too much like a vibrator (sus).
This is the closest I got: https://www.amazon.com/dp/B09NNFPHXG https://www.amazon.com/dp/B0CD7FPFQ5?th=1
Some of the Mi Bands work pretty well with GadgetBridge, which would block their ability to phone home. There’s a list is compatible devices somewhere on the GadgetBridge wiki.
Throw in a leg strap, and this becomes the best bang-for-the-buck solution.