Pacer is a smartphone-based fitness tracker, meaning that participants are not required to purchase separate, often costly wearable fitness trackers. Participants need only to carry their smartphones with them as they start stepping. In addition, if a participant should forget her phone, Pacer & P4T allows manually added participant data to be considered in the challenge rules, should Admins allow it. Pacer does connect and work with some wearables; see the article How can my challenge participants connect their wearables to Pacer? for more information.