You may already yell at passengers and other road users, but it's time to learn a new vocabulary. Shout "Minikit" at this battery-powered gadget from Parrot (HK$949) and you have instant control over your smartphone. Follow that with the name of who you want to speak to, and the connection is instant. Incoming calls need only a brief "accept" or "reject" command. It uses Bluetooth to connect to up to two smartphones, so both the driver and a passenger can join in.
A good value step up from an FM transmitter, the Aircast Auto (HK$780) allows basic hands-free calling and plays music on a smartphone through the car stereo. Answering calls means clicking a button, and music requires a cable. Pairing over Bluetooth is quick, there's a USB slot to recharge a smartphone, and a separate microphone can be mounted anywhere on the dashboard for maximum voice sensitivity. It works with all brands of smartphones, but voice control is possible only with an iPhone.