There's a payment provider doing something similar called "Sofortüberweisung" (translates to "instant (bank) transfer"). It is pretty popular in Germany, AFAIK they only support banks from Germany (and maybe some neighbouring countries).
They go a step further and actually transfer the funds from your bank account via Online banking after you provide them with your login and TAN.
Quite scary to be honest, to me at least. It's basically a scraper/bot that initiates the transfer for you, pretending to be you, without the bank's knowledge. While forwarding your login information and TANs to third parties is by most banks considered a violation of their ToS, they don't seem to be willing to do anything about it (probably because of Sofortüberweisung's popularity with their customers).
If I understood correctly, you use the login to verify the account information and to check whether funds are available. The transfer is initiated via ACH.
Sofortüberweisung doesn't use ACH (or SEPA), they actually transfer the money via Online banking using a bot pretending to be the account owner.
It's popular because SEPA transfers are really cheap, compared to paying with credit cards.
Last time I paid with SOFORT I noticed that they hadn't committed the wire transfer. KLM issued me with my flight tickets, but the wire transfer was sitting in the outbox and could have been cancelled. Not sure what happens if I cancel a payment like that - does the merchant get notified and cancel the flight tickets too?
They go a step further and actually transfer the funds from your bank account via Online banking after you provide them with your login and TAN.
Quite scary to be honest, to me at least. It's basically a scraper/bot that initiates the transfer for you, pretending to be you, without the bank's knowledge. While forwarding your login information and TANs to third parties is by most banks considered a violation of their ToS, they don't seem to be willing to do anything about it (probably because of Sofortüberweisung's popularity with their customers).