I have do-less goals to track some finances, spending less money in my pocket and limiting budget on clothes. They work fine and are easy to understand, each day Beeminder add budget on my road and I have to stay under the road. When I get money from ATM or buy clothes I add them to my road. I know at each moment how much I can spend.
I did a lot of savings thanks to Beeminder !!!
So I think you must give to everybody the option to create a do-less budget goal.