Stand alone trailer with linkage to extend driving range for X, S or Model 3.
Utility trailer or Uhaul type trailer, can get power assist braking features, additional protection for battery.
PW incorporated into the design of a motor home, ideally in the ftame for low Centre of gravity. The ultimate RV accessory to render noisy gas powered generator at the camp site obselete.
RV with solar roof of course is an ideal companion to the built in Power wall capacity...
Nothing revolutionary there, but have not Sen or heard of yet. Would love to see.