<prompt> Human: In particular it would be nice to have an app iosandroid that reminded you when it was time to rebalance, had information for tax efficiency, a way to calculate the collective volitility and expected returns of a group of mutual funds, make suggestions based one risk tolerance etc. Does something like that exist?Edit: I should mention that I ask this question since I am considering working on such an app. But as robert_bradly mentions perhaps Vanguard already has this covered.  <response>: Vanguard has a pretty awesome set of tools including adding in outside investments for a complete picture. Im sure Fidelity and others to do. 