I have been using Linode.com hosting services for several years now. That is where I keep my VPS with sites / projects and for various personal purposes.
They have an API, and as far as I understand, they built an iPhone client on top of it.
The client looks like it was just reskinned.
You log in and see the list of all your servers. In my case there is only 1 :)
Tap the server and you see the first bit of beauty. The VPS can be rebooted or even powered off entirely.
Next come graphs for CPU load, traffic, and disk activity. They show activity either for the last 8 hours or for the last 2 weeks. In practice that is usually more than enough.
You can also connect over SSH right there (although some SSH client has to be installed on the iPhone; otherwise it complains). Under the SSH button there is a LISH Console button — that is something like a web console. In other words, there is a built-in SSH client. You can quickly log in and restart a crashed Nginx, for example.
There is an edit server button, but there you can only rename it and assign it to some group.
But that is far from all.
There is a left-side menu with items like these. From the client you can manage DNS records, for example.
There is also access to their knowledge base.
A list of articles by topic; the article itself opens in the built-in browser. The knowledge base is not offline, of course, but overall it is a useful thing (probably). In any case, it will not hurt.
And the final items in the left-side menu are balance, traffic quota statistics, and even the ability to enter a new credit card. In the About section you can call technical support.
The app looks non-native and probably written in something like PhoneGap, but it is still useful. Must have if you host on Linode.