Look who's calling
When a customer calls my mobile, I don't have foggiest who they are and the first bit of the call can be a bit stuttery as I try to remember who it is and what school.
How about having the hubspot app sync with your contact list so that when a customer in your hubspot calls it shows you the customers name and company. At least that way you have a few seconds to rack your brain for their details.
Going one further, if you open the hubspot app while on the phone to that customer it takes you straight to their details/ activity.