If you are talking about compressor/condenser units to add to an existing box, then there isn't any new technology because this was figured out a long time ago with hermetically sealed inverter-drive compressors, variable speed controllers, etc.
If you are looking for a drop-in complete unit, then the standard home ones have become more efficient - particularly if you can source European units.
As always, box insulation is king, and a well-matched holding plate to a compressor is more efficient than an evaporator plate.
Oz Fridge, represented in the US by Rich Boren is another efficient unit to consider:
About Rich -
Mark