App to manage application "workspaces"

Hi everyone,

I'm wondering if anyone knows of an app that would help me out a lot.

The idea is that you create "workspaces", and then whitelist apps that can be managed by the main app. Using the main app you can switch between these "workspaces", which will open/close apps based on the workspace you've chosen. e.g. I could have a work workspace (Chrome Canary, Sublime Text, Dash), a play workspace (Chrome, Steam, Adium, Tweetbot), a writing workspace (Word, Dictionary, Chrome) etc.

It would close other apps that you have told the main app to "manage" (e.g. switching from "play" to "writing" would close Steam, Adium and Tweetbot and open Word and Dictionary)

I'd also like some other features, such as changing default browser etc., but they're a bonus.

If this doesn't exist I think I'd quite like to try building it myself, but there's no point building something that's already out there!

Thanks,
Josep Duffy