SmartThings Has added support for the 4 button Ecosmart handheld remote. This is a zigbee battery powered device available in both the US and Canada at Home Depot. Uses one CR2450 battery.
Low price, usually under $20 for the remote and an included smart bulb. It goes in and out of stock a lot, and you may have to buy one at a nearby store.
you don’t need any custom code for it. And you can control any device that works with the hub, not just zigbee devices. 
Please ask any further questions about it in the following device specific discussion thread: