“There’s a web app for that” is a chrome extension that lets you find apps from the Chrome Web Store without visiting the store. When you browse the web pages the extension just displays a plus icon if the site has an chrome web app in the chrome web store.
“Discovery (i.e., how a user finds apps to install) is an interesting aspect of app stores. In some ways, discovery is not necessary: a significant appeal of the store is that it catalogs all the apps, so if the user is looking for a to do list or Twitter client, it’s pretty obvious what to search for. However, that assumes that the user has a specific need in mind already, and is aware that that class of application exists,” explains Mihai, the author of the app.
The start page after you install displays your most visited sites that have chrome web app in the chrome app store.
This app helps sometimes finding the real chrome app of the sites rather than hooking up with some unofficial chrome apps. Most apps on the chrome web store are just shortcuts that let you jump to the site easily from the new tab page.