These have been going on sale a lot lately, so here is another one! It seems this is a boxing day sale and currently online only, which is fine given you want to use Cashrewards of course! Otherwise if you want to purchase in store, Officeworks price match is $123.50.
Dick Smith also have the same price (given this is run by Dick Smith at David Jones anyway): http://www.dicksmith.com.au/fitbit-charge-hr However Dick Smith don't have Cashrewards.
Buy DJ gift cards @Woolies for an extra discount.