I think I may have suggested something similar and more convoluted a while back, but I don't think it ended up going anywhere. Basically, all it would do is when a redstone signal is applied it would send items to the left or the right depending on how you've got the "output" set. And when the redstone signal is off it acts like a normal conveyor belt. Would be very useful in setting up multiple metal presses on a single conveyor line and not have a separate line for each metal press stamp.

Splitter & Turntable can accomplish this to an adequate degree.

Even better yet just have this change effect the already made conveyor splitter

How about a simple multi-block structure, conveyor belt, piston facing the way you want things pushed, and a red-stone control atop that. The conveyor piston has two modes, item-sort w/ both blacklist and whitelist settings or red-stone pulse control.