Try this
I can also play the pipes while riding, played the pipes competitively for years.
One of my old favorites was doing my best to look as busy as possible. Headphones on, burger in one hand, cell phone in the other. People got out of my way. They were 'fraid.
Used to jump rope while riding.
As a beginner, I could not ride and talk at the same time. Unicycling took so much concentration, I could only form very simple, short sentences. Playing the guitar and riding is pretty easy. The way the guitar sticks out… is good for balance. Someone posted a video, a couple years ago, of them playing the soprano sax while riding. Several friends have asked if I can play the bassoon and ride simultaneously. The chance of damaging my face or equipment is too great.
Playing a fretted instrument (other than a viola da gamba) is easy while riding, harder while idling. Ditto for singing: idling gets you a tiny bit more out of breath than riding does. Or maybe it’s the twisting of your torso, I don’t know, but anyway, if you’re gonna perform a song on your uni for a crowd, one possibility is to sing the most important bits while idling, so you can “stand” and face your audience for emphasis. For the rest of the song, riding in circles allows you to catch your breath a little.
I can… Hold a conversation, give a wave/thumbs up/middle finger (depending on he situation) to drivers on the road, sip water, point my light properly, check my Garmin… I think that’s about it 
I have jump mounted in Flippers that are for snorkeling. www.instagram.com/azraguse88 don’t know how I stayed on 
It happens rarely now… but had a guy throw an apple at my head while on my 36… Well it ended quiet nasty it made me come off broke my heal. He also ended up in hospital I live in a friendly area now
Now there’s an idea - I know somebody who has one of those (and I should be able to play a tune on one, I’m sure I’ve played a tuba at some point). It has to be done…
I was going to say that I can play a trumpet whilst riding - I was thinking of getting a trombone partly because it would look far more impressive playing that whilst riding (riding a giraffe natch), but then a Sousa is way better. The only obvious downside (apart from making mounting a giraffe even harder) is that they’re a lot, lot more expensive.
As for riding vs idling, playing trumpet whilst riding is almost trivial, idling a lot harder.
High Five
Just the other day I managed to give a random passerby a high five. Usually this results in me losing control and bailing spectacularly (quite embarrassing), so i generally avoid it, but this guy surprised me and it worked.
Other than that, walking my dog and carrying groceries (beer) are about the most impressive things I can do while riding.
A UPD while playing a sousaphone would be rather awkward . 
I’ve done that a couple of times recently when riding my giraffe - to a chap riding an electric longboard! I did point out that it was a low 5 for me though 
When I was in the early learning phase, I could talk about trivial things. But when my wife asked me if I knew a route to take on another trip, I found I could not think anything involving spatial concepts - my mind was purely blank! It seems as if spatial thinking was completely occupied by unicycling.
Now I am confident I could even learn to do the Rubiks Cube while riding. Probably I will do several UPDs before I manage to do so.
Anyone here with experience in the "uni and cube "-learning process who can give advice?
Hendrik
I can’t speak to the cube part, but the uni part just involves getting comfortable with idling. Or riding, but you might not have a lot of space, especially if you have an audience. Someone just did this, either on the Gong Show or on America’s Got Talent. And I think he was blindfolded.
Once your riding gets more solid, that will be the easy part. At least from the point of view of someone that hasn’t learned to solve a Rubik’s cube… 
That’s one thing I can’t do at all: shut my eyes for longer than one second while riding.
There are vestibular, somatosensory, and visual systems of balance. As a beginner, I could not close my eyes, and it was difficult to ride in relative darkness. When I improved, the non-visual forms of balance improved, and I was able to close my eyes. Keep practicing, and you will get there!
Text!
Could it get more dangerous? 