This paper presents a low-complexity compression scheme of electrocardiogram (ECG) signals based on the Haar wavelet transform (HWT) for use on mobile devices. An experimental, wearable, multi-lead ECG monitor was also developed and served as a testing platform for the proposed compression scheme. The proposed scheme was applied to all 48 recordings of the MIT-BIH arrhythmia database, where a percent root mean square difference (PRD) of 3.11 along with a compression ratio (CR) of 21.38:1 was achieved on average. The proposed scheme was also tested using raw multi-lead captures from the experimental device where an average PRD and CR of 9.77 and 24.95:1 was achieved respectively. The proposed HWT based compression scheme was efficiently implemented on a mobile platform and is capable of compressing multi-lead ECG signals, allowing for efficient data management in the context of data storage or data transmission.