Boss GT units have it and can combine (assign) with other effects (like EQ or volume) to the expression pedal. Toss in some guitar tone control on the swell and you're there. I get some great "whale song" from my GT3 with Slow and a volume pedal. Bring on the reverb.
I really want to try an Ebow, however.
I once thought a "Sweeping Arpeggio" was an Italian janitor.