I think your confusion is about how the Tip Jar app works. It isn't like the Ohmibod that each tip triggers it. So she doesn't have to look at the screen or have the machine plugged to her computer for the show.
The Tip Jar app works like this:
1) You set a goal, say 500 tokens to "fill the Tip Jar"
2) You set up a speed of the Tip Jar depletion... say, 50 tokens per minute.
3) Once the goal is met the show begins.
4) While the show is going the Tip Jar will deplete at a 50 tokens per minute rate.
5) Every tip people give through the show will be added to the Tip Jar and will extend the show.
5) Once the Tip Jar is empty, the show is over.
In this example, the show begins with 500 tokens so if the depletion rate is 50 tokens per minute that means the minimum amount of time the show will last is 10 minutes, if nobody tips her. But every time someone tips 50 tokens it extends the show one more minute. The point is for the room to keep tipping while the show is on.
In the fuck machine example you gave us, she doesn't need to look at her computer all that much because she knows exactly how long the show will last unless she receives more tips. So a glance here and there is enough for her to know when the show will be over.
Even though it sounds like a fantastic idea, I have never found a way to make the Tip Jar work for me. Maybe it is the pressure of seeing the tokens running out, like it was a private show, that makes members be on edge and less likely to tip. Who knows.