Google+ Photos has preliminary chromecast support in the works.

Right now it's disabled, but the app_name it searches for is "801a5db5-9903-4613-a8e2-3ddb1226cedd" which will be the first app (aside from the homescreen) that uses a hash for the app_name instead of a predefined name! This could mean that Google+ Photos uses the regular app registration process, and this could be a sign that chromecast sdk will be coming out of preview soonish!
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