Windows Azure Mobile
-- My favorite ones are in the order of preference following :
Appcelerator (currently using it )
App42 ( tried it )
Stackmob (tried it )
I have probably tried everyone one of those on the list, and a lot of it really depends which SDK some of those services offer.
Edit: a "Firebase vs Parse" question on Quora  (it's the first answer, no login required) made me realize that Parse is much more "mobile first" (tm), with a "full service" for mobile apps, whereas Firebase is taking "just" a subset (a very big subset) of data persistence, authentication and data security (e.g. server-less apps, which can be used in also in Mobile apps, but things like push notifications etc are more "role your own")