The easiest example of this being something like a nail gun that runs off tubing linked to a compressor that's small enough to be carted around by hand.  It takes maybe 5-10 minutes to load, and then tops itself off when depleted, which generally takes only a few minutes of continous use.

Where you have existing, natural features that could be used to store large amounts of compressed air you could conceibly use them as a massive version of the compressor that you can cart around by hand. And with smart grid technology, you can use this to push down peak electric loads.

What I'd be most interested to know is if there's a way to apply the same principle to fluids.  Greater density would seem to apply the same power storage in a much smaller area.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg