Just to be clear, this is completely fake! It's a goof you can play on your students, especially during Valentine's Day!
What you're going to want to do is bring up two students and have them sit next to each other. Then you're going to, "hook them up" to a fake device. This can be anything. I like to use headbands with a little blue light on the front. Some people like to use old bicycle helmets with wires coming out of them. The choice is yours. You're just putting on a show to make it look like they're being hooked up to this compatibility tester.
Once they're hooked up, explain that the Compatibility Tester reads a bunch of different vital signs to determine if you like or dislike something. Turn on one of the machines and give an example like, "Pizza". Have the needles go to 100%. Then say, "Pineapple on pizza" and have the needles immediately drop down to 0%. Then explain that when both sides of the machine are on, the gauge in the middle will tell us how compatible the two people are.
Turn on the other person's machine and begin reading off a list of things. Every group is different. You know your ministry, so this is a fantastic chance to use inside jokes. You're just going to read off ideas/things/phrases to see what their response is. A great good is saying, "Dungeons and Dragons", but making the girl's meters go way up while guy's goes down.
When you're done, you can just say, "What's their overall compatibility?" and have the person running the computer pick the percentage by moving the mouse around.
On the tech side of things, the meter levels are all controlled by the position of the mouse. When you're in the game's dashboard, click on the control icon in the sidebar. You'll see a rectangle split up into 4 parts. Hovering your mouse over this rectangle will affect the needles in the game. The 1st person is controlled by where the mouse is going left to right. The further right you move, the closer to 100% that person will get. The 2nd person is controlled by where they mouse is going up and down. The closer to the top, the closer to 100% that second person will get.
When you combine the two, you can see that moving the mouse to the top-right corner of the rectangle will make both people positive. Moving to the bottom-left will make them both negative. Moving to the other two corners will make one positive and one negative. The gauge in the middle is looking for similarity. So, both being negative will result is better compatibility. They become less compatible when one person is positive while the other is negative.