Has anyone tried this i-lock? It's not clear if it can be used on all or most seatposts and wheels. Wonder if it's sold in the U.S.?

Looked at the video- it looks like a waste of money. There's nothing preventing a thief from picking up the bike and walking away with it. He could then cut off the seatpost at his leisure.

Meh, even if you're in a rush, a good u-lock can do this faster and better.

I think it might make a good secondary, or tertiary back up lock. I wouldn't want it for a primary lock.

Goofy idea

Ok idea for securing your seat/post and rear wheel,but I would still use a U lock up front.

That looks ok for free-locking for when you'll be gone for a moment or two. Why not just use one of these for free-locking?

Agreed. IMO the ring lock is more convenient and costs less. Some also now can be used with a cable or chain that attaches to the ring lock for securing the front wheel or securing the bike to a fixed object. Most frames are not designed for the seatpost quick release to be operated hundreds to thousands of times, flexing the top of the seat tube, so I would worry about frame failure in that area too.