Thanks BitMaxz
In short
there is no good segwit wallet exist.
Not with all your requirements.
Elecrum is by far the best wallet that has support for Segwit at the moment. But like you said, there is currently no iOS version available.
GreenAdress does have cross platform and support for Segwit. But it is a multisig wallet, which means that (AFAIK) you don't have access to all the private-keys.
Armory is way more secure if you know how to use it, it's less user-friendly than Electrum. It has SegWit implemented, allows you to manage your keys and does support sweeping. For android, I assume you use it as a portable device, you don't need to have an advanced wallet like Armory, just use it to store small amounts of Bitcoin for doing micro transactions. Every web-wallet that allows you to see your private would be fine for that.