A few comments that I hope are constructive. Looking at your page, I'm not confident you're avoiding the issue by which these tools proliferate:
https://xkcd.com/927/
Your users and their clients are still going to be using Slack and email, but it seems like you're giving me one more thing to log into. You write:
> Schedule your time spent and group distracting reminders and notifications in one place
If this "one place" is a separate silo from Slack, Outlook, Basecamp, Skype, SMS, Discord, Hipchat, IRC, and Github...it's not the one place I'll need to check. It's the n+1th place.
Now, if I can put my credentials into Calmbird (securely would be nice, but you can have the plaintext if you can make this insanity stop) and have it do the API connection to - or, if necessary, the nasty DOM-manipulation, Windows message hacking, and client-impersonating - to put all these services and their notifications in one place, that would be a solution to the proliferation problem.
Also:
> schedule automatic emails to your clients with updates
My clients don't want automatic emails, especially from templates/digests. They want me to hand-craft them as if it was the most important thing in my life. And while they can understand a curt update message or a missed daily status notification, the real point of these updates are to confirm that I'm still on the project. If a message accidentally went out with a placeholder like "I'm still working on {todo-insert-task-here}", and I didn't know about it, that would be...bad.