IEMs, especially Chinese IEMs. In my opinion, analog audio technology has reached its 'good enough' level long time ago, so now it is all about making it efficient.

IEMs has been flourishing recently, with two perspective. One is high-end and the other is 'cheap but good'. Chinese IEMs are in both group, and doing very well. Other major audio manufacturers are also doing it but not as fast as them.

Headphones seems like reached its 'okay... what now?' status. However, wireless headphones are different story. It used to be sound okay and reasonably priced but now they are trying to be high-end.