Sellf is a hybrid CRM that offers access to most if not all of a CRMs expected features via Mobile App, Browser, OS, Slack, and whatever else you want via Zapier; Sellf installs instantly and is ready to use on any major platform PC, tablet, or smartphone.
If you already use Slack then I urge you to consider Sellf even more-so because Sellf can be closely integrated with and operated from within Slack.
Sellf allows for a ton of integrations, see them at http://sellfapp.com/integrations/
In addition to this Sellf did win "Most Innovative App of 2015"
I've used Sellf with Slack, and I must say, it works Flawlessly