Very nice. Simple and effective.
However, am a little concerned regarding some health & safety issues - which are taken very seriously here in uk at any rate; by the HSE (Health and Safety Executive.)
Just imagine - you're holding onto the saw, with the bungee under some tension; perhaps stretched further than is wise.
Then, say something startles you - perhaps a 'static' shock referred to in other posts - you let go of the tool in surprise.
Whizz, bang, whallop - the saw flies across the work-shop as the bungee suddenly contracts.
Maybe the glass in door / windows could be broken, the clock knocked off the wall - etc, etc.
Would strongly suggest wearing a full face helmet, as important PPE (Personal Protective Equipment) as it might even hit your head.
Also, might consider (as far as possible) encasing the saw in a thick protective rubber casing - to reduce any potential damage.
In addition it might be prudent to wear, say, goal-keepers gloves - these might help you to catch the tool (as it flies about) thus reducing consequential damage.
In addition, perhaps worth considering some of damping system, so the bungee doesn't freely bounce up and down in such circumstances.
Should you allow others to use the bungee solution, would also suggest they attend a one day training course - unfortunately, at great expense.
That might help to protect you (legally) if someone didn't follow correct operational procedures.
Were you in the UK, the HSE would be pleased to arrange for risk assessment of the equipment set-up; probably at great expense as well.
Richard