SMS Stats is a cydia app that tallies all the texts on your phone, including SMS texts and iMessage. It calculates a running total divided into Sent, Received SMS, and iMessage, and also can pull up your top contact as well how many messages for that contact have been sent and received. Theres a mode for tracking the monthly tally of texts received as well as a mode which provides messaging stats for each of your contacts.

It is free from the BigBoss repo.