Philips Hue is the most well-known smart lighting brand, but it's been a little behind on features. Until now, the only way to group lights was within rooms. With the latest app update, you can finally create custom groups, known as Hue Zones.
In the new Hue app update, you can choose to create a new Zone from the room screen. This can include lights from multiple rooms, or several lights from the same room. The latter seems more useful as you can more easily control fixtures with multiple bulbs in a single tap.
Oddly, you can't add existing rooms to a Zone—you have to add each new light to a Zone individually. The feature is still listed as beta in the app, so hopefully the process gets streamlined in the future.