If you want to start a robot company, plan to kick off by selling a service performed by robots, not the robots themselves. That was the message of robot startup founders and investors speaking at HAX demo day this week. HAX is a five-year-old hardware accelerator based in Shenzhen, China, and San Francisco. "I'm a big fan of going out and doing a service with a robot, competing with other businesses that provide that service, rather than trying to sell a $100,000 robot," said Nathan Harding, co-founder of Ekso Bionics and now co-founder and CEO of Wink Robotics, a still-mostly-stealthy company intending to bring robotics technology into the beauty salon industry. "So," Harding continued, "if you design a bricklaying robot, go out and bid on projects that involve laying bricks….