[Hidden Desires]

Ok, so I've thought about this for a while, and while there are probably easier and safer ways to do this, I feel like this would be a possible way. Note, I have no idea how to rig this up, but here is an idea to get you started.

As you said, the issue with a lot of forced dares is that you can simply bypass the actual eating part by just moving the scat. The best of these dares at least require you to use your mouth, but that still doesn't require consumption.

What I propose is fairly simple. You know how there are pressure plates in puzzles in video games, where you need to put something of a correct weight on the platform to trigger a door lock? What if we did the opposite?

Essentially, if you, or anyone, can figure out a way rig a scale to a release method, we have a starting point. Hypothetically, lets say we have one pound of weight loaded on a scale (such as a kitchen scale). You could rig a release in some fashion to where when the weight goes down past 1/2 pound, then the release triggers.

This still doesn't solve the problem you describe though. You can still have your shit on the scale and just move it off. That's where the second part comes into play. For it to work, you will need to make sure your shit is liquid, such as an enema you have released. Next, you will need a long hose or straw from it to your mouth. Third, you must be bound in such a way that you can reach the released key when you trigger it, but cannot manipulate the scale or scat itself. Fourth, and this is key to forcing it, you need to have a cone around your neck similar to a dog that's had surgery. Tape it around the neck so you have no leakage, and tie the cone itself with string to an anchor on the ceiling.

What this essentially does, is makes it so that once you start, you are unable to get the key until you trigger the release. You can't physically reach the scale, so you have to drink the scat liquid through a straw. You can't just spit it out though, because you have a cone around your head preventing you spitting it out. Even if you spit it out into the cone, because the strings are anchoring it to the ceiling, you can't get it to knock over to spill on the floor, so you can only spit into the cone so much before it gets up to your nose and would drown you.

Alternatively, instead of the cone, you could tape your mouth shut around the hose, but I don't like that idea in case you have to vomit. At any rate, a secondary release should be allowed, but at a punishment of some sort.)
Here is a diagram, that kinda explains my logic. I know it's all over the place lol.