Considering that my boyfriend proposed to me last year on Valentine’s Day (in the bathtub, no less) one might assume 2010 would be a tough act to follow. Not so, however, because I love these nifty heart-shaped handwarmers he gave me: they’re practical, whimsical, and even a little nerdy, thanks to the science behind them. Add to this the fact that they are resuseable, and for me, that’s a winning combo. Yes, Valentine’s Day came early in our house simply because – while it has been cold lately – it could easily be 80 degrees here in Texas by the…