Amazon.com has plenty of reviews.... they're mostly positive.
Far as the CC review of MPH being way off... well, the device has two modes.
Real World and Hotwheel.
Real World is actual MPH/KPH.
Hotwheel mode is for 1/64 scale hotwheels...so speed recorded is multiplied by 64. so a Hotwheel going 10mph (fast) will register 640mph! 🙂
I'd definetly grab one if you can... great fun, or an excellent gift.... Seattle and Portland area CCs are sold out... not avail on-line either.. too bad..