A non-uniformly spaced digital FIR filter bank has been proposed for QRS detection in wearable biomedical devices in Body Area Network (BAN) applications. The proposed filter bank is constructed based on frequency-response masking technique and employs two half-band filters as prototype filters, which leads to significant savings in terms of arithmetic operations. The introduction of non-uniformly spaced filter bank further enhances the detection accuracy especially in the BAN applications where motion artifacts are a major concern. Simulations show that the proposed algorithm correctly detects the QRS of both resting and exercising ECG, even under the presence of severe motion artifacts, baseline drift and large P/T waves.