I use a python script to download most transactions from banks/credit cards. https://sites.google.com/site/pocketsense/home/msmoneyfixp1/...
There are enough people who do this that you can figure out how to access the OFX endpoint for most financial institutions.
One problem I have with relying on OFX is that I have a nagging suspicion that it's not as 'official' as the statements. If there were a discrepancy between the two, I'd worry that I wouldn't be able to resolve it in my favor without having reviewed (and thus downloaded and reconciled against) the statements.
I really think the state of how bad consumer bank integration tech is has led to this reality of login and scrape that you have with yodlee & co.
Otherwise, it requires only an email (and that you pay them 5$/monthly somehow. Paypal, credit card, whatever).
If you don't want auto-import (which doesn't even work for my credit union anyway), you can uploads .csvs, or manually input your transactions.
LWN have a current "Grumpy Editor" series article on Beancount:
https://lwn.net/Articles/751874/
And an older one from 2009: