Vysr founder and CEO Guda Venkatesh says he wants the platform to be a veritable (and ultimately profitable) sandbox for developers.
The add-on tucks a small sidebar in the corner of your browser, letting you highlight text and quickly search various Web services to find out more--all without leaving the page.
Lately, I've seen a few publishing services that let content creators do this (see Apture and Zemanta) , but Vysr's solution is more voluntary, and it is aimed at users who want to look things up from very targeted services without having to rely on the built-in search box in their browser. To a certain degree, Vysr is an attempt to ween users off of the search box, for the sake of productivity.
Venkatesh says it will be an uphill battle to attract developers to build and maintain plug-ins, but after having watched Facebook's platform launch, he told me that he thinks the overall simplicity of building a Vysr application will attract bootstrapped developers who have put more care and finesse into their applications.
One of the new applications for today is a music search module that will look up any word or track name you highlight, then cross-reference it with GrooveShark Lite. When found, it will play the track in the corner of your browser while you continue to surf around, making it a pretty good addition to something like reading an album review.
As mentioned earlier, Vysr will eventually have ads as part of the equation. According to Venkatesh, they'll only be on the little application overlay windows--not on the sidebar itself--meaning that you won't be randomly surfing a page and getting advertisements. My guess is that most people will be willing to tolerate ads for convenience's sake.
If you're a developer looking to get your service integrated, you can check out the documentation here. Venkatesh says it took only 10 minutes to port over GrooveShark, so you might be able to get yours done during a bathroom break.