Do you get cold sweats with the hypo?
If so, there's this gadget which alarms and phones people if your wrist gets too cold and damp.
https://www.hypoband.co.uk
Obviously wouldn't stop a hypo altogether but the idea seems to be that it will alarm early on before it gets way too low.
I bought one but ironically enough the only times I've had cold sweats is when I've not been wearing it!
Just a one-off cost unlike dexcom which is a contnuing monthly payment.