Is there a product that accurately measures calories burned through out a day?

i am sure that a Heart Rate Monitor would be fairly inaccurate cuz it doesn't know why my heart rate is up... unless you burn tons of calories wen you get scared, excited or any other kind of adrenaline rush. I am looking for something that i can wear all day that will let me know how many calories i am burning currently weather exercising, watching tv, playing Wii, or typing etc. and also keep a running tally for the day. or if that's not realistic, you know would cost a million bucks, then maybe a HRM that measures even when HR is low