Shortly after my last post I did a web search to see if any local businesses carry the Uni-Jack just so I could see one in person, and found the local Fleet Farm carries them. Next time I was in the store I took a look, and found they were on sale! $69.99 for the 4000# model, or Amazon price without any shipping costs, so I bought one thinking I might return it.
I held onto it, and used it for the first time today to change the battery in my daughter's Dodge Journey. Yes, you need a jack to change the battery. It's mounted behind the front bumper and accessed through the wheelwell, so the tire has to come off. The jack worked great. I did use my floor jack to lift the vehicle a little before getting the Uni-Jack out. It probably isn't short enough to get under most vehicles to change a flat, but it's great for other work. My only complaint is, it didn't go down the last 1 1/2" and was still tight under the car when I lowered the car, so I had to use the floor jack to get the Uni-Jack out. Don't know what the problem was, as I was able to push it down by hand after it was out. I guess it needs pressure to completely collapse vs continuing to collapse on its own when the valve is open.