Adding statcounter to WordPress

I’m thinking about using the free statcounter service on my site, but it requires that I add a little bit of javascript to each page. If I was running a single theme, I could probably find all the appropriate </body> tags and just paste in the statcounter code. But I’m trying to support multiple themes; besides, where’s the fun in cutting and pasting a bunch of code? Also, what if I need to change the statcounter code for some reason? So I think the Right Thing to do here is come up with a plugin for the wp_footer action which will insert some user-specified code, (in this case, my statcounter javascript). I haven’t found a plugin for statcounter, so I’ll be searching for a generic footer plugin. If I can’t find anything, I guess I’ll have to roll my own.