I use one called RemoteHD (http://www.remotehd.com/Mac/) for the iphone, I downloaded it instead of forking out for a wireless keyboard for when my laptops rigged to my projector, it works fine for quick internet browsing. Another thing it allows me to do is connect over 3g so I can stream video or audio from my mac at home while I'm out and about in the car or whatnot.
LogMeIn Ignition is a great app for accessing your computer with an Android phone, although the price tag probably puts a lot of people off.
Used it to access my computer at home, while in Spain earlier last year and it worked flawlessly
Alternatively, try Teamviewer. It's free for the time being, but not available through the Market due to being a fully featured Beta.LogMeIn Ignition is a great app for accessing your computer with an Android phone, although the price tag probably puts a lot of people off.
This what I purchased a few weeks ago and it is a nifty bit of kit to be honest - the only problem I found with it over one month now is that I had to reset the bluetooth paring once, but apart from that it is great for sitting back on your sofa and watching the TV. Another little bit of software I have is for the mouse pointer as sometimes it is a bit hard to see the pointer so I use Magnifying Glass Pro to Magnify a circle around the pointer.