Hello I am building an ionic app that send transaction to ethereum smart contract. in web I used metmask but what is the alternative for mobile? is possible to run an ethereum client in a mobile?
Yes it is possible. Basically it’s the same as building a web dapp. The only difference is that you need to explicitly specify the Web3 Provider to point out to a running remote node. And you need to sign transactions explicitly (no metamask to so this for you). Let me know shall you need further details.
In case you are looking for a generic ethereum client implemented with Ionic, I released a simple POC on Github: https://github.com/mottolini/ionic-ethereum