There are some nice services out there (for example https://github.com/guibranco/progressbar) that will generate a statusbar based on the URL requested. This is nice, but seems a bit silly to spend the CPU cycles generating the bar each time, though I assume its deployed with a cache, and I guess there's some minor risk of spyware or similar.
So, I thought I'd just make the svg files for the progress bars in advance, and then serve them up as needed. I used & modified Guilherme's code to generate these files - thanks!
Or if you're Batman