In this paper, we present work in progress on application scenario where a smartphone is used to detect and quantitatively index early signs of asthma attack triggered by exercise. Here, the embedded microphone in the mobile phone records the user's breath sound while motion sensors-accelerometer, gyroscope and digital compass provide measurements on the level or intensity of activity and posture changes. Our design and preliminary result show that using only built-in sensors in smartphones, mobile phones can sufficiently and reliably monitor health status of patients with long-term respiratory conditions such as asthma.