WordPress.org

What on earth is Intercom and what is a CRM?

Take a look at http://intercom.io, they explain it better than I can!

Does this plugin track all visitors to my site?

No, it only tracks logged-in users. The administrator is also not tracked.

Can I use private key authentication (user hash)?

Absolutely! In fact this is highly recommended for security reasons.

Can I customise the inbox link?

Yes, you can choose the label text.

Can I choose the format of the username sent to Intercom?

Yes, you can choose between "Firstname Lastname" or the user's displayname.

Can I send other custom data?

Yes, if you wish you can send the user's role, ID and website URL.

Does this plugin work on older versions of WordPress or PHP?

Possibly, but I've not tried. I can't provide support if you're using WordPress 3.2.1 or older, or PHP older than 5.2.4.