I've wanted to get a Fernandes Sustainer or similar unit in my guitar for a while, just so I could do that sort of thing. This is a big reason why I want a Moog guitar or lap steel, too. Or, at least an eBow.
For the record, those are still on my wish list, too, but from the looks of things, if I had a Fender Runaway, it could do most of what I'd want all that for. I'm not sure how it works, but it seems like a variant of compression and likely to want to be at the front of my pedal chain, toward the right side (not just because of the way guitar pedals go, but also because I'm right-footed and would rather have wah, volume and this right next to each other in front of my right foot, no matter what way things are wired.
These aren't in stores yet, as far as I can tell, but I'm waiting with decreasing patience for them to show.