I work in the ED and I love it. Pays better than what I would make on the truck (AMR and Acadian are the only ones that higher Basics in Austin) and I know that I am learning a lot more than I would if I were working for a transport service.
A quick list of my duties, off the top of my head:
Making beds
Drawing blood (straight stick, but the few paramedic techs start lines when we're slammed)
Cleaning pee and poop off patients
Patient comfort issues (fetching blankets, water/ice chips if not NPO)
Stocking supplies
Making beds
Helping restrain/keep an eye on combative intox/psych/in-custody patients
Compressions during codes (bagging too, until Resp. shows up)
Putting in/taking out Foley caths
Vital signs
Splinting/casting
Dressing wounds
EKG monitor lead placement
Making beds
Setting up Suture/LP/Chest Tube/Whatever trays
Assisting with Suture/LP/Chest Tube/misc. sterile procedures
Chaperoning doctors/nurses with certain types of patient
Helping bring patients from the helipad
Sitting in the triage window recept-ing (something techs probably shouldn't do when RNs are available)
Translating (only one in the dept. that's full spanish bilingual, except for one of the registration gals )
Running to and from lab with stuff they're afraid will spill in the tube system (blood, CSF, poop)
Making beds
And finally, the most important one of all: Being an extra set of hands. Because that is what being an ER tech is all about. Just as a large part of the nurses' job is to be the hands that carry out the MDs' orders, your job is to do what the nurses and MDs tell you. Honestly, you're pretty much a scutmonkey as a tech. However, few of the staff will treat you that way, especially since you're an EMT (some of the staff will be jaded by working with CNAs at best, lay-volunteers-turned-techs at worst).
That's probably the hardest part of being a tech, and one of the things they won't really outright teach you: it can be a difficult thing to balance wanting to be as helpful as possible to the folks with licenses, with not letting yourself be taken advantage of or treated disrespectfully.
Still, don't let me scare you: it's a blast. The patients often love you, since you're the one bringing warm blankets and not sticking them with needles as often as everyone else. It's an amazing learning environment, both in terms of your co-workers and the variety and sheer quantity of patients you will see. No one should be a tech as a career, but it's a great intro to the field to see if caring for patients is really your thing, as well as dealing with the icky stuff that comes with EMS.
You asked this question a few months back: did you get the job? How's it going?