OFX is an XML'ish protocol that all of the big banks and major banking software (MS Money, Quicken, Quickbooks, iBank, etc.) use to communicate when downloading transactions, posting checks, doing transfers, etc. it's what i'm using for downloading bank transactions in corduroy (http://corduroysite.com/) and i have hundreds of banks listed in there.
if you know a bank's OFX URL, you can just send it an OFX query and download transactions. it works the same for every bank and credit card company, and it's much quicker than the screen-scraping dance of establishing a session, logging in, clicking around, and then updating your scripts every time the website updates its interface.
here are some common OFX servers: http://wiki.gnucash.org/wiki/OFX_Direct_Connect_Bank_Setting...
On the flip side, any SAAS that monitored your bank transactions would likely be more interested in developing and selling a profile of you than protecting you.
I'd love to automate telegraphic transfer payments ("wiring" the money). Just need to poll for when the money arrives, and send out the receipt. Currently, you have to check manually.
That said, telegraphic transfer payments often to involve a fair bit of rigmarole, including negotiating prices, and even contractual terms in some cases. So maybe automating that bit wouldn't make much difference. Still, it would be great.
A number of other UK banks there too.