What information can people get from a tumblr ip tracker?

On an iPod, iPhone, pc?

Tumbler IP tracker? Not a clue. Never used it. I think http://statcounter.com/ is similar to that. I know what happens when someone assumes but anyways that shows the IP address, internet provider, operating system, browser, entry and exit time and a few other non-personal tidbits.

They get your IP. The IP gives them the location of your ISP. Mine is invariably wrong: same IP in different IP locators put me in the 2 nearby cities and one even puts me in the next county.

Nevertheless if that's someone whom you know or knew to expect you they could know you visited their website and how often and how long you spent there and whatever else poster #1 told you.