Apple's iPad is a great device for the typical road warrior: it allows you to check email and browse websites; it has apps for contact and project management, allows you to edit and create documents, and more. For the road warrior that also administers various servers, the one thing the iPad lacks is a good terminal. Let's face it, a good administrator will need to be able to access a command line at some point when managing remote servers. A good web interface like cPanel will only get you so far if Apache dies.
There are a few SSH applications available for the iPad. The two that I have used are iSSH and Panic's Prompt (a recent new-comer to the SSH apps for iPad and iPhone). Both of these are great applications, and each offers something the other doesn't. While neither is a terminal program that runs on the iPad, they do allow for a terminal interface to a remote server.
iSSH is quite nice, and has been around longer. You can use it to remotely login to a computer using your account password, or you can create a keypair in the app and email it to yourself to install on the server to use public key authentication. Well, you're supposed to be able to — as of version 4.6, this doesn't seem to be the case.
What iSSH also fully supports, unlike Prompt, is terminal managers like GNU screen. With it you can ssh into a box, type screen -x and be able to navigate around the session as if you were at a computer. I also appreciate how it handles the keyboard. Because the iPad screen is quite small compared to a computer screen, handling that real-estate as efficiently as possible is necessary. Because what is shown on the screen will quickly be covered by the on-screen keyboard, the transparent "underlay" of the keyboard that can be had by tapping the keyboard icon at the top of the screen is useful (but sometimes a little hard to see on a busy screen). It also helps to reduce the font size (found in General settings), and you can change the transparency of the keyboard as well, to find the balance between being able to see the contents of the screen and the keyboard.
iSSH does a lot more than just that. It is also can make VNC connections (even over SSH), and can do telnet or raw connections in addition to SSH. It also has the ability to create SSH tunnels.
Panic's Prompt, on the other hand, is quite a bit less powerful but a little more elegant. Prompt is only an SSH client; if you need the VNC and X server, the ability to telnet and so forth, you definitely want iSSH. But the adjustment of the screen, on whether or not the keyboard is present, is a fantastic feature in Prompt.
If you need to see the whole screen, you can minimize the keyboard and the screen will adjust; when you need the keyboard, the screen shifts up so you always see exactly where you are and what you are typing (unlike iSSH which covers up what you are typing if you do not have the transparent keyboard active).
Prompt also uses Bonjour technology to locate available SSH servers located close by, listed under Shared Servers. Like iSSH it supports using public keys, but unlike iSSH it does not generate them on the device so you will need to generate your key on your desktop and use iTunes to sync it over to Prompt using File Sharing (select the iPad in iTunes, when it is connected, and navigate to the Apps tab to do so).
Both applications fully support using a bluetooth keyboard, which is great.
Prompt is $4.99 and iSSH is $9.99; if you just need an SSH client then Prompt is a good choice. If you need something really flexible with a lot of power and productivity, for double the price of Prompt you're getting about 10x the functionality. But for some, that functionality may be unnecessary, so that's an extra $5 wasted. Out of the two, I prefer the look and feel of Prompt, but appreciate the extra power that iSSH provides. Keep in mind, however, that Prompt was just released, so expect the functionality to grow as the product matures.
Vincent Danen works on the Red Hat Security Response Team and lives in Canada. He has been writing about and developing on Linux for over 10 years and is a veteran Mac user.