Propeller Health has developed a system which includes a sensor that can attach to both rescue and controller inhalers and an Asthma Health Platform [29]. The inhaler sensor collects date and time of inhaler use and number of puffs taken. This data is transferred via Bluetooth® technology to the Asthma Health Platform on a mobile device and can be matched with GPS coordinates obtained from the mobile device. The Asthma Health Platform can also be used to record asthma symptoms and triggers which integrates with other data streams such as weather, pollen counts, and pollution. The Propeller Health System is one of the most studied to date. A 4-month pilot study conducted in 30 individuals showed when the device and app were used along with weekly feedback, participants had an improvement in asthma control and a decline in day-to-day asthma symptoms [30]. The effectiveness of Propeller Health System on rescue inhaler has also been examined [31••]. In a study of 495 patients, all patients received the Propeller Health System but only 250 received sensor-based feedback. The authors found a decrease in mean daily rescue medication use in those receiving sensor-based feedback (0.19 vs. 0.25 in control arm) which was more pronounced in patients with uncontrolled asthma at baseline. These findings were confirmed in another study of 120 participants with a decrease in rescue medication use by 39% and an increase in symptom-free days by 12% [32]. Propeller Health has also developed a provider-facing web interface (portal) that allows providers and their staff to view patient medication use and asthma control status. This is available to providers that enroll their patients with the Propeller Health System but can be integrated into existing EMR systems to allow for data sharing among providers. Merchant et al. evaluated this enhanced Propeller Health System and found a decrease in asthma-related emergency department visits and hospitalizations [33].