Are there any existing native libraries (not whole wallets, I do not need a UI but want to sign transactions and call smart contract functions embedded in another app) for iOS or Android? If not, are there efforts currently ongoing or what is the closest I could get right now?
Ethereum Mobile Wallet – Best Library for iOS and Android Development
androidioslibrarymobile-wallet
Best Answer
There are some guys who are running geth on Android and iOS. you could find the libs and the apk project. But seriously, you need to wait the light protocol client because it is a bit insane to use a full client (Many Go of storage + so many writes that it will use battery and storage longevity).
Look this:
Android
The geth with LES is in test currently. I have made few benchmarks:
iOS
gethfunctionality: web3swift