A device is provided that includes a housing and a mount configured to mount the housing to a wrist of a wearer. The device also includes a first electrical contact disposed on an inner surface of the mount and configured to contact skin at a first external body surface. The device also includes a second electrical contact disposed on an outer surface of the mount and configured to be contacted by skin of a second external body surface. The device also includes a signal conditioner disposed in the housing. The signal conditioner is configured to determine data indicative of a biological state of the wearer based on voltage fluctuations between the first electrical contact and the second electrical contact.