LightWallet is a serviceable money tracker, with Google export/import

From the Nokia Store description:

LightWallet is a lightweight but effective user friendly solution for transaction tracking and personal finance management using your mobile phone. LightWallet supports multiple accounts, user-defined transaction categories, embedded calculator, transaction filtering, monthly reports, backup and restore using MS Excel (CSV) files and Google Docs spreadsheets.

Here's LightWallet in action:

A 'wallet' is effectively an account, of course - it doesn't have to be a physical wallet of any kind! You can have as many as you like, ditto categories; (right) the interface is heavily menu-based - you'll be needing 'Add' a lot - I can only think that the J2ME implementation restricted the developer from putting a shortcut to this function on the toolbar....

Long pressing on accounts or transactions does offer basic functionality, as shown here; (right) adding in a new expense.

As with other money management applications, you can transfer funds at any point between wallets (accounts) if needed; (right) pick lists are shown for wallets, categories and charge/income.

The import/export facilities are surprisingly effective for such a lightweight application - being able to poke (admittedly text only) information into a Google Spreadsheet, for example.

The J2ME, menu-centric interface takes some getting used to, especially when getting started and faced with almost blank screens and no wallets, categories or transactions. However, persevere and the application soon starts to make sense. Although lightweight in concept, there's the flexibility to clear months as you go (presumably reconciling with bank statements), plus import and export facilities. 

In practice, every time I've ever started to record transactions and attempt a proper wallet 'book keeping' system, I've failed - the matching up of accounting month start/end times, the transactions which overflow, the failing to input some transactions which then throws everything off.... The exercise quickly becomes a lot of work and not worth it for most people - I just scan my online or paper statements each month and mentally recognise the names of transactions of any significant amount and I'm done. 

However, there are people who loves to track every expense or income, plus this could be very easily used as an expense tracker for business 'claim back' purposes. Comments welcome if you've used it in the past.

One footnote: somewhat curiously, LightWallet is listed as 'open source', despite the £1.50 price tag in the Store, and indeed the code is all online here - which means that you could theoretically take the source and build it yourself. And, being J2ME, this is presumably fairly trivial, though it's still doubtful that anyone would go to the bother, to save such a small sum. And you can't blame the developer for wanting to make a little pocket money from pre-packaging the app in the Nokia Store - it just looks a little odd to see the 'open source' presence at the same time?