Maybe if you get a part time job and can pay for it yourself from your earnings it may impress them that you are goal oriented. I’m 46 and the only way I can support my hobby habits is by doing side work so it doesn’t remove funds from our household budget.
id still go with a trusty 2x4. but thats just me. 
Tell them you want to take up skydiving. They’ll tell you it’s too expensive and dangerous. Then you say “So how about unicycling?”
Seriously, probably the best way is to get the unicyle yourself. I would guess they probably don’t care so much if you unicycle, but don’t want to go spend a bunch of money on it, either.
If you have CraigsList in your area, maybe run an ad looking for a free unicycle. Couldn’t hurt. There’s plenty of them stashed away unused.
Hahahhahahahahaha zing
First of all do your parents watch any TV? If so, nuff said.
Secondly, if your parents actually do think unicycling is a stupid waste of time, remind them that stupid wastes of time are an essential part of life. Without them all the rest would be quite overwhelming.
And for the record, I am a parent. (How successful though depends on whom you talk to.)
I am also a parent and my younger son taught me to unicycle.
A Note To Parents About Unicycling
Hello. My name is Stephen. I’m a 47-year-old parent. I’d like to tell you a little bit about unicycling and your kid.
I never thought much about unicycles when I was a kid. I didn’t even know anyone that rode one. But just recently, I started riding a unicycle for the first time ever. It’s been some hard work and a lot of fun. I wish I had started earlier in life. Maybe you have a kid and you’re wondering if he or she should take up unicycling.
Kids have several options as to how they spend their leisure time. The most popular is probably video games. Second most popular is perhaps television. So it’s no surprise that we’re raising a whole generation of couch potatoes. And of course there’s always drugs and crime and other alternatives that parents don’t like to think about. I think that for the right kid, unicycling is a wonderful alternative to the above. It motivates you to learn, to practice, to get exercise, to get out of the house, and to top it all off, it’s fun. What more could a parent wish for their kids?
Is unicycling dangerous? That’s one of the first questions I asked before I started. I had never known a unicyclist, never watched anyone learn, and didn’t really know what to expect, so I asked around some. But what I found, from asking around and from my own experience, is that unicycling is fairly safe. When you ride a unicycle, you’re pretty much in a walking position already. Most of the time, when you “fall”, you don’t actually fall down. The unicycle simply shoots out ahead of or behind you and you find yourself on your feet again. In learning, I have actually fallen down a few times, and banged my knee once. But all in all, I’ve had more serious injuries jogging (sprained ankle), skating in a skating rink (sprained ankle), learning to ride a bicycle as a kid (several) and mowing a yard (projectile injury) than what I’ve had while learning to unicycle. Pads and helmet can help avoid problems, though not absolutely essential. People can and do take unicycling to extreme levels that involve a greater amount of hazard, but this is also true of bicycle riding, automobile driving, snow skiing, or many other activities.
Is unicycling hard? People ask me that sometimes when I’m riding. It takes practice, a good bit in my case. It’s harder than learning to bicycle. I started out going up and down the hall, with hands on the wall, and then rode beside fences or railings, holding onto them, until I was able to ride down the street. Once you learn to ride a little bit, each different thing you do requires more practice, rather unlike a bicycle. But as far as I can tell, most people that have the desire and the patience also have the ability to unicycle. A person that is not especially interested is not too likely to learn. And I suppose some people just learn faster than others, too.
Is unicycling expensive? The cost can vary but tends to be pretty reasonable. I spent around $100 for the unicycle that my son and I are both riding. That’s a fair bit of money. But compared to the hours and hours we’ve spent on it, it’s been a real bargain for us, and I recently bought a second shorter unicycle for my daughter. A good unicycle is cheaper than a good bicycle. I spent less on that unicycle than I did on my bicycle, or our computer, or our television, or the aquarium we once had, or the cell phone my wife has, or my son’s electric guitar. For the price of a good video game console and a few games, you can buy a really first class unicycle.
Is there any point to unicycling? Why do it? There are a few people that commute on unicycles, or work as professional entertainers with them. But for most of us, unicycling is simply an immensely enjoyable recreation. As with any recreation, it may seem pointless to someone who isn’t interested in it. Many activities that other people like are not at all appealing to me- reading romance novels, say, or watching television, or going to movies or dancing or bowling or team sports or any number of other things. But each serves its purpose as recreation for different people, and unicycling just happens to be one recreation that appeals to me. It is just a really wonderful experience to go balancing down the road. People I’ve never met speak to me or watch me. There’s a sense of accomplishment each time I ride farther or make it past a more difficult spot. And it’s all good exercise.
Should your kid have a unicycle? I think the key to that is the amount of interest he or she shows in the idea. Unlike a lot of other activities, unicycling require some work to learn. I would be hesitant to buy one as a gift for a kid that never expressed an interest in it. If you don’t know if your kid would be interested or not, ask. If they seem mildly curious but not enthused, my guess is they’re unlikely to pursue it once they spend the first half-hour trying it. If they are enthralled by idea, then go for it.
Where do I get a unicycle? What kind? There are a couple of resources that can be very helpful. One is the website www.unicycling.org. I find it unique that I can go on that website as a beginner unicyclist, ask a question, and get responses from some of the best riders in the world. One source of unicycles is www.unicycle.com. Your local bicycle store may also sell unicycles, although the sales staff may not know one from another. There are some sellers of new unicycles on Ebay as well, although you need to know what you are looking at to purchase there, as the quality of the products does vary.