A Web Of Apps
techcrunch.com
techcrunch.com
good, useful apps do not have a discoverability problem. it isn't hard to find the evernote app. i go to their website and get a link to it, or i type it in to the search box in the market. it is much more difficult to find an evernote rip-off, but why would i want to do that?
i find the list of obscure startup names tackling the app discovery problem to be fairly telling. if i've never heard of your discovery service, i won't be discovering much on it. they need to solve their own discovery problem before they attempt to solve anybody else's.
For location-based discovery, imagine you go into Home Depot, and the app that lets you self scan in products and self check out automatically gets pushed down to you (or notifies you to be available). That sort of thing doesn't happen yet, and there is certainly opportunities for innovation.
This is particular bad for games. What is the best game? It really depends on the user taste. Sites like Kongregate apply usual recommendation algorithms to ease this, which, I believe, is a nice first step in the right direction[2].
[1] http://www.kongregate.com/
[2] http://venturebeat.com/2007/11/11/facebook-search-expands-wi...
The most visible, useful, example of URL schemes is Facebook SSO. When a user logs into your app using you Facebook credentials they are redirected to the Facebook app (or website) where it authorises your app and then uses your apps URL scheme to return the user back.