As a huge Mint.com fan I'm having a hard time figuring out why I would use this. I also have the Android app which lets me see a whole bunch of info about my budget automatically.
Is your target market people without smart phones? I could see this working with them. My biggest worry would be the fact people are lazy when it comes to budgets. I know I am. I like Mint.com because I can spend like normal without manually tracking it and eventually they send me an SMS saying STOP SPENDING MONEY. :)
My target market so far is indeed people without smartphones, as well as couples - that's why I've got the little 'members' tab for keeping track of a budget collaboratively.
When I first set out to build it, I had to consider whether to make it something you hook up to your bank accounts, or something you manage yourself - I went the self managed route, because it lets you track things like cash on hand in addition to money in your bank account.
Smartphones (which I'll define as anything with a keyboard that doesn't require you to do T9 input) are now so cheap that there is close to a 1:1 overlap between "smartphone owners" and "people who do anything with their phone other than talk on it".
I think this goes right to your addressable market: I'm concerned that you might be creating a cool, useful application for a non-web savvy, non-phone savvy market.
Is your target market people without smart phones? I could see this working with them. My biggest worry would be the fact people are lazy when it comes to budgets. I know I am. I like Mint.com because I can spend like normal without manually tracking it and eventually they send me an SMS saying STOP SPENDING MONEY. :)