Ethan,
Hammers aren't as isolating as doing wrist curls, but in my world, any focus on arms directly is isolation. I don't use much isolation until a foundation is in place, and that usually results from several weeks of intense training of the core. By core I am not referring to lots of abs, such as a Pilates/Yoga class. I am referring to exercises done from the core such as squats, bench press, chin-ups, dead lifts, etc. Your extremities get plenty of arm work on those type exercises.
Ozz, don't worry about building your lower arms. If you follow a protocol like the what I recommended, plus you don't use crutches as I mentioned above, your forearms will grow. They don't get enough benefit from iso exercises to warrant wasting valuable time in the gym. Try doing some heavy deadlifts and don't use straps and tell me if you think your forearms will get a workout.