I ran some small test with phonegap and it compiles apk data.Quite useful.
BUT:
If you want to release at google play you definitely need a signed apk-file.I think no one should do this step in the cloud! I mean, its your choice, but who can say, whats happening with your data on other peoples servers?! I dont trust it....
I would like to know about signed apk-file, it makes me wonder about my data on other peoples server, is a cloud? i think it's for testing purpose, not a final product...