what kind of material should i start with to make prototype bluetooth headset casing ? Answered

Start with play dough (clay) to get a suitable shape.

Then depending on the sophistication of the finished product I would go for sugru or shape lock plastic Or a mould and fiberglass/carbon fibre sheet.

Wood or Plexiglass will be good for making the casing for a prototype.Both of them have their pro's & con's . Prexiglass is a bit difficult to work with but will last a good time, Wood is easy to work with but may not last long enough, Just for the info wood's are of 2 types Hard wood & Soft wood ,so choose your material wisely