How accurated is my new HRM? Sportsline duo i060

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I just purchased this HRM yesterday and use it this morning. I am more confused now...my HRM said I burned 226 calories by walking/running for 47min. My Nike +ipod said I burned 354 caloies and MFP said 433 calories. I would assume that the heart rate monitor is probably the most accurete but is way off. Anyone have any advise for me? Does anyone have this HRM?