Matthew Miller seems to like SplashMoney for Windows Mobile, over at ZDNet blog "The Mobile Gadgeteer."
"I have a simple budget spreadsheet I use, but to get spending under control you really need to track your transactions closer than I have been. I am starting to use SplashMoney to track and analyze my spending so I can see where my money is going and try to come up with a better strategy for spending and saving."
