Trauma/EMS/ED volunteering involving "contact" depends a lot on your situation and how much they'll let you do. Personally, if you've already escorted, I'd go to your volunteer director/supervisor/coordinator, tell them what you want, and ask how to get it. EMS could mean spending a lot of time sitting around, ED could mean a lot of time staying out of the way, and trauma could be a lot of errand running (take these films, samples, etc.....).
I literally dickered w/ an admissions rep over this for awhile (I was polite, but really) because I failed to see the difference between sitting at an info desk in a hospital and teaching (she actually suggested info desk as a "clinical" experience). Either way, you're only dealing with people who are well enough to get over to you and ask a question, and actually, in my classroom, I'm Way more likely to get barfed on, or to escort someone to the bathroom, than I am in the hospital. I have to decide all the time whether someone is sick enough to merit a phone call to mom, or enough to require mom to take the kid home, or hurt enough to need a squad. At the hospital, I just get to ask/tell a nurse who is right there, and poof, I've passed the buck.
That said, I'm on med/surg, and sometimes renal, and I get a lot of pt. interaction. Inpatient is great, because the pts are typically happy to have people come and check in who aren't going to try to take blood or "work on them", I've found it more interesting that the outpatient stuff I've done because the patients talk to you more....read, lots of things I could talk about in an interview.
I think the same would be true of hospice, or of geriatric work in general, or of a service where you checked in on people in their homes, or were somehow required to interview patients (there are some agencies in our area that have volunteers do this, and some paid research jobs). Older pts are pretty likely to tell me what I think I should do with myself, and to be highly opinionated about health care, as well as experienced with "the system" -they compare/contrast different floors, doctors, hospitals.