don't know if there's a pedal that'll do that, Edge used a prototype guitar with a sustainer device on the original recording. that original guitar cost a lot of money and had a lot of electronics in it. nowadays there's the Fernandes sustainer which fits into the guitar, and comes on a number of Fernandes guitars. it can sustain the note infinitely (well, until the battery runs out!) and can switch between holding the original note or an harmonic feedback mode.
if you look in Drac's thread on his new build guitar it has one fitted.