Are Trådfri motion detectors, dimmers, and switch compatible with HomeKit?
To see what's currently compatible with HomeKit have a look at HomeKit accessories.
The list keeps getting smarter,, at Apple's website.

At the present time, nothing from Ikea is compatible and will not be until later this year in the fall, starting with Ikea's Trådfri line of smart lighting. Explicit compatibility of any other Ikea products has yet to be announced.