Sure a visitor counter would be possible.
Don't think there is a package for that.
Sow how could you create a counter.
-Step 1 where to store the visits:
Create a property visits on the document type
or store the visits in a new db table
-Step 2 update the visits on page load
Best way to do this is to use base and ajax
http://umbraco.org/documentation/books/introduction-to-baseOr you could install umbraco stats ... and create a usercontrol that gets the visits ..
http://umbracostats.umbraco.net/Cheers,
Tim
Umbraco tips and tricks:
http://www.nibble.be - umbraco mvp 08/09 - certified level 1 & 2 professional