Apple - Looking for an iPhone SSH app
Prompt for iOS
Prompt allows you to remotely SSH into another machine. Without jailbreaking, there is no way to use Terminal to access your file system. However, I've found that if you do jailbreak your phone and want to use Prompt as a Terminal, you can set it to SSH to server 127.0.0.1
and authenticate with the standard iPhone root credentials.
Remoter: Remote Desktop (VNC) for iOS
This app does basically the same thing just a little differently. By default it allows a VNC connection for screen sharing, but it has different add ons that you can purchase that allow SSH, Telnet, and RDP.
I use Rove Mobile Admin Client on my iPhone. It's free, there are no annoying in-app ads, and it comes with an SSH client which I use to connect to machines at work while I'm on the road. Works great. It's quite possible to run a remote emacs editor and send all the control characters you need.