Always loved the idea of a pair of seemingly normal undies, Slowly weakening someone's control, and with the slightest accident (like a small leak before reaching the toilet) the underwear changes slightly. A pad forming. Each slight accident becomes worse as the underwear changes more and more.

I think it's female voice TTS (Text To Speech)

Your underwear gradually puffs out into pampers as thick as theirs, your words of desperate protest diminishing in clarity as the regressive disease takes hold. You feel their drool continue to collect on you, burbling whimpers as you lay stuck under their hefty huggies, drooling yourself now too..