Readwise - Effortlessly rediscover and organize your Kindle highlights

Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.

Clippings.io - Organize the notes you make on your Kindle

Boomerang for Outlook - Boomerang for Outlook offers email productivity tools to track, schedule and send mails at the right time.

Klib - Kindle & iBooks Highlights Manager

Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.