Drift

• Chatbots can automatically qualify sales leads and push the most valuable conversations to sales reps.
• Connect Drift to your calendar to allow automatic meeting scheduling.
• Drift Sequences lets you setup automated sales emails that use machine learning and NLP to automatically opt-out people who aren't interested in your offer.

Basic functionality is available on the free plan, with paid plans offering addition email, playbook and automation features.

You can simply add a small code snippet to get Drift up and running on your website, however you will need a developer if you want a more complex setup that tracks users.