I travel a great deal and am always torn as to whether, and which of my four, to take a computer with me. As the capabilities of my phones have improved, I have made more and longer trips without a laptop.
I have had WebExPCNow on two computers for $14.95 per month but have been reluctant to pay $15 more to be able to access all three computers from the iPhone. Ignition is a good fit for me. The iPhone software is $30 but that is one-time and covers all four of my computers with the free version of Logmein. (I expect to pay $19.95 per month for the Professional version which includes drag-n-drop file sharing and remote printing.)
The problem of course is representing the desktop on this little screen. Part of the solution is to permit dynamic panning and resizing. Another trick is to keep the cursor in the middle of the iPhone screen and move the controls to it. The best trick of all is to make all of this quick and smooth. It really is an elegant solution.
Even if I were not using Apple dollars to pay for this app, I would still be happy with the price. If you want the function, this is the right software.
(Did I say that it works over GPRS? But do not tell "the steaming pile of failure.")