I would like to be able to control a spigot based on whether or not there is a connection to an inlet. Basically, for a given inlet, I'd like to be able to turn off all other inputs if a connection is made to it, and open that back up when the connection is deleted.

This seems easy enough to do if I use lists to flag where connections are coming from and check for that "type" flag at the point of input, but the issue is when I get rid of that connection, there's no way to tell pd to switch back to accepting other inputs.

Does this make any sense? If there was an object that put out a 1 or 0 depending on if anything was connected to its inlet, I'd be all happy.

Perhaps [iemguts/canvasconnections] is helpful?

Something like this
inlet-default-value.pd

Thanks @alexandros and @FFW, this is just what I needed! Seems like running a [metro 1] through a message to [canvasconnections] is even pretty inexpensive, so it's not hard to have this actively turn that spigot on and off depending on if a connection is made. Now to make this work constantly across a variable number of inlets!

I've whipped up a little abstraction for this purpose. Posted to the abstraction section here.