Citibank wanted to develop their own digital coin, I don't know if it will be tradable for BTC. I heard Barklays was also thinking in a possible integration. Other than that Banks accept BTC indirectly...
Some banks are also interested in creating their own blockchain ,but there is no point in it cause bitcoin is here to eliminate them and free the people from the unnecessary control's over transactions and uses.
however, all the services that the banks could offer people are already available in bitcoin world today and with much ease.
Edit : Coinbase and bitcoincryptobank.com could be the closest.(never used them though.)