DHT11 / clearWatch error weird behavior

Looks good, just a lil' bit hacked ( var _this = this; and later var ht = this;). I'd keep it the same variable in both lines - I like to use "var self = this;" as it works without underscore.

Maybe a disconnect function would be nice, to remove the watch when no longer needed. But memory is limited, and I don't think that anyone would ever use it. Unless trying to connect different devices to the same pin, which would be a bad design, better using I2C instead.