1) A liability waiver like the one you describe will protect them from liability IF the device is correctly manufactured and designed and the instructions for use are correct, but you misuse it in some fashion or it is damaged after delivery to you. However, a company cannot protect themself from product liability for dangerous or improper manufacture, design, or instructions.2) However, if the company is based in China, even if you had a viable legal claim against them, you might have no recourse--suing a foreign company and collecting money from them, especially a Chinese company (since Chinese law, their legal system, and their government are all slanted in favor of their businesses and citizens) can be very expensive and difficult.