I use the same wrist type I used when running on my bike and on my rower. I just made a "wrist" from foam and strapped it on. I use it for training, which means I let it tell me how hard to work, as well as to tell me how hard I am working. I found a website that describes how to do this, so I'll just refer you there.
Running 101: Training With A Heart Rate Monitor - Competitor Running