I would love a live view of the account balance. By this I mean that when I scroll through my chronology, the account balance is displayed at the relevant time. For example, if I scroll through August, my account balance is shown at the beginning and if I scroll further and look at my incoming and outgoing transactions, the displayed amount is updated by the corresponding sum until I arrive at the current time and my current balance is displayed.
I've seen this before at another online bank and found it very practical for me personally and made it easier to keep track of my account history.