We've released a first round of features around IP Addresses. Similar to how you can see the history by Person, you can now see the history by IP address. If you're tracking down an issue affecting logged-out users, this can be really helpful.
To get there, click on an IP address anywhere in the Rollbar interface:
You'll be able to see all events affecting that IP:
There's also a handy link to the WHOIS record for the IP.