This could encompass many things for an entrepreneur; investors, possible hires, sales leads, etc. I'd prefer a service that is a mainly mobile based.
For mainly mobile based, take a look at Base CRM (getbase.com) and RelateIQ (relateiq.com). They both do a good job in helping you managing your contacts, leads, investors etc. while also automatically synchronizing all your email communications right into the CRM.
For non-mobile, check out close.io, which is the best inside sales tool on the market today (Primarily for sales teams selling over phone and email) and logs calls and emails automatically and cuts out data entry.
