Here is a rugged robotic platform capable of towing a heavy pick up truck weighing about 6500 lbs. The Stealth Super Mega Bot has high-torque motors and a modular design. These robots are remotely operated and can be used indoors and outside. They weigh 225 lbs each and have a max speed of 15 mph.
You can add cameras and other modules to do more with your robot. The above video shows the Super Mega Bot towing a Ford F-250 Super Duty truck. More information is available here.