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
A phone won’t vibrate strongly enough for you? You could adjust the intensity of those you know
Nah they’re right. My Xiaomi had great vibration, audible without a ringtone but my Pixel now is very weak. Definitely depends on the brand and model.