Connecting a load sensor and a few Hall-effect sensors

Yes - the sensor can be used (with a suitable ADC), but because it's only half a wheatstone bridge it's not going to have such good accuracy (one day the reading could be different to the next).

For using a digital scale, I think it'll depend which model you have. However a scale like this one would be perfect - you can get a simple square wave, the duty cycle of which is the weight.

Putting that into Espruino is trivial - just connect up to any IO, and the software looks like:

setWatch(function(e) {
  var weight = (e.time-e.lastTime)*someScaleFactor;
}, YOUR_PIN, { repeat: true, edge: 'falling' });