The Roland VB99 (and I think GR55) has an advanced version of the Boss effect which tracks and processes each string separately, you can even pan them and apply separate reverbs and eq to each. I’ve got a fretless patch set up with the on-board bass assignable knob for varying the high cut which goves a great variety of sounds. Weirdly because it sounds so good I start playing like I’m on a fretless, too.