The instructions say the wireless fork leg sensor and the handle bar unit should be w/in about 2' of each other. Easily done on a mini.
The fork leg sensor and the handlebar unit each has its own battery. They're expensive like camera batteries and they normally don't match, so a 2-pack doesn't help. At least they last a long time.
The type that has a wire running up the fork leg is much less expensive, only needs one battery and will probably have all the same other features. I think you can get a cheap wire-type unit for less than 20 bucks. The skinny little wire will probably last OK on a mini because it doesn't have to tolerate the 12" stroke of a dirt bike fork. That's what killed my buddy's. It fatigued from the flexing.
On both types the magnet is designed to clamp to a spoke and needs to pass very close by the sensor. If your bike has steel or mag wheels, the challenge will be finding an effective way to attach the magnet to the wheel so it stays put and meets the sensor clearance requirement. I'd use JB Weld or 2-part epoxy stick.
There's always a chance that it just won't fit, discovered only after you've got JB Weld all over the magnet and can't take it back to the store. That's why I'd start w/the cheaper, wired-type. Try to take a look at one already attached to a bicycle.