Tough call. The Tummy Shield was designed by an Australian dad, who spent years coming up with a way to prevent injuries to a fetus in the event a pregnant woman is in a car crash. An injury like the brain trauma his first daughter had when he and his pregnant wife were in a car crash.
It is a sit-on platform with a hook that's meant to hold the belt across a woman's thighs instead of across her belly. The Tummy Shield website says it has "undergone vigorous tests in some of Australia’s leading testing facilities, including crash tests at high speeds."
It's not like they're totally off base with this thing; studies show that up to 3% of women are in car accidents while pregnant, and even minor traumas can cause adverse pregnancy and birth outcomes.
Even though there's no studies on it, I'd really like to believe that the Tummy Shield works. I'd like to believe that all the time, effort and attention that didn't go into the rambling website, with its misspellings and unsourced, non-specific claims, went into making the Tummy Shield as safe and effective as it needs to be. But there's no way of knowing that, short of coughing up $188 for the thing and driving into a mailbox. And that, I don't want to find out.