As You can see on top right of this blog, JPU just tell You if your operations inside this page have a cost for your CPU.
For example, try to click one mini-banner on the right side (OCS - DCS) and look at JPU monitor during fade in/out.
The better browser I've tested is Opera but FireFox and Internet Explorer seems to work nicely too :-)
If You want to add a JPU in your site, just use a script tag like this one:
JPU - by WebReflection
If You just want to test JPU inside another site, using FireFox or uriscript compatible browser, just use this lik.
Please remember that JPU is just for fun, about 0.5 Kb and quite totally unobtrusive.
Have fun with JPU :D
Here You can view a demo page comparing them with your Operating System CPU monitor (not so different in my case :D)