So for now the Ethereum promise to have a distributed network where I don't need to trust any man in the middle is really not possible yet on mobile devices?
In theory, you could run a private client on DigitalOcean and then connect to that. Apart from that, true light clients are coming [1].
Particularly interesting is this comment by the ethereum light client developer: [2]
"Can't promise anything yet but we're not that far from real trustless O(1) light client syncing."
[2] https://www.reddit.com/r/ethereum/comments/5x27ss/after_metr... They may even
[1] https://blog.ethereum.org/2017/01/07/introduction-light-clie...