Accompany - Accompany platform integrates with email, contacts, social feeds and more to keep you informed on your professional connections.
Referral Candy - Run a fully automated, customizable and easy to integrate referral program for ecommerce.
Propeller CRM - Small business CRM with deep Gmail integration
Ambassador - Referral Automation, Made Simple.
Streak - Manage customers inside Gmail
ReferralRocket.io - Referral Program Software for SaaS