It is a good bit different. But, if you've seen guys doing track stands on a fixed gear bike with no hands, that's fairly similar. The unicycle is still going to require more adjustments and balancing.
Unicycling is nothing like riding a bike no handed and is more like walking. On most higher end unicycles they have a handle on the front to hold onto to do hops, but you can also learn no-handed hopping where you squeeze the saddle with your legs to hold it. There is a more difficult way to hop as well where you have the seat in front of you and hold the side of it. This allows you to be able to tuck better and get higher hops.
On a bike you do not consider the front to back balance much. It is only used to transfer traction from the front wheel to back. This is even when riding no handed.
Riding a unicycle requires you to know where your balance is at all times. Unicyclists can tell you where their balance is relative to the centre of the hub. It is a lot simpler and purer.
If you can find it, there are some videos about of a swiss guy called Julien Money. He is absolutely amazing! his knowledge of balance is almost god like!