I don't use any doorbell app that the manufactures offer with their hardware. They all have to use an outside server to work and I simply don't want to be "married" to any of them - for cost, privacy and security reasons.
I do have BI set up to automatically text me a snapshot from the doorbell whenever it is triggered (as defined in BI, not the doorbell, so it can be tweaked to be more reliable). I can also pull up the doorbell cameras using the BI app and my mobile devices through a VPN server set up on my own networking equipment. I won't have two way audio doing this (only one way - I can hear, but not speak), but I personally think answering a doorbell via software is a horrible idea because it pretty much tells the person that you are not at home. If I simply don't answer it, they might assume I'm not home, but can't be 100% sure - maybe I'm taking a nap, etc.