I second that if you want accurate, and especially during workouts - you gotta get a heart rate monitor with a chest strap. A lot of those fitbits/nikebands/jawbones are essentially glorified pedometers, and all they know is that you're moving - not how fast or how much energy you're using or anything else. I just got a Polar heart rate monitor (the FT7), and have found that SP was underestimating my calorie burn by about 700 calories per week - it was hugely motivating to see that a run where I really exerted myself wasn't 220 calories - it was 420!
It won't count your all day calories - but to be fair just about nothing will without plugging in estimates. You could just as easily make that estimate for much cheaper.