The premed committee at my college required me to submit 4 letters of recommendation to the committee - 2 letters from science faculty, 1 letter from a professor in the humanities, and 1 letter from a medical professional. These letters were packaged with the letter from the premed committee that was written by the chairmen of the committee. So the adcoms at the med schools where I applied got a total of 5 letters, including the committee letter.
The letter from the premed committee basically compared my strengths as an applicant with other current and past applicants from my college. For example, am I regarded by the committee as being in the top ten percent of the pool of med school applicants from my college, etc....does the committee regard me as an outstanding applicant, a strong applicant, an average applicant, or a below average applicant, in comparison with the normal pool of med school applicants from my college, that kind of thing.
Oh, and my premed committee also required a personal interview with the committee that actually was good preparation for med school interviews. The process worked well for me and was helpful in getting multiple acceptances.