Hi,

There is a Bitfinex app for your iDevices on the Apple store.
It's 100% free to use with some advertising.

Just enter your API keys and you can begin to trade.
There is only 2 type of trade for the moment, trade limit and trade market.

Link:
https://itunes.apple.com/us/app/bitfinex/id969062318?l=fr&ls=1&mt=8

It's in the same design as the Bittrex app (https://itunes.apple.com/us/app/bittrex/id932961087?l=fr&ls=1&mt=8).