[Atriya]

I'm shopping for an IEM, and I'd like to go wireless. Most wireless IEM manufacturers (Jaybird, Plantronics, Beats, etc) seem to be marketing convenience, waterproofness, workout-friendliness, etc, and not sound quality. The regular 'audiophile' manufacturers e.g. Sennheiser, HiFiMan, etc seem to be not making wireless IEMs at all.
 
My question is: is there a wireless IEM capable of at least entry-level audiophile sound quality - for example comparable to a HiFiMan RE-400 or Senn Momentum In-Ear or Fiio EX1? If so, what is your recommendation for the best sounding wireless IEM (under about $300)?

 

[WhiteKnite]

Best bet currently is to get an Apt-X capable lanyard (if you have an apt-x capable source) and attach it to whatever removable cable iems you want (assuming compatible connectors).  Otherwise the trinity phantom true wireless sets look somewhat promising.
 
Just keep in mind even with apt-x you won't quite match the quality of a wired connection from a decent source so keep your expectations reasonable.  I currently use a trinity mmcx lanyard with my SE425 at the gym and though FAR better than my freshebuds pro I wouldn't use it for critical listening. 
 
The new Fiio lanyard is due out soon, and it might be a good idea to wait and see how good that is.  On paper it looks like it could have reasonable good performance.

 

[Atriya]

  Best bet currently is to get an Apt-X capable lanyard (if you have an apt-x capable source) and attach it to whatever removable cable iems you want (assuming compatible connectors).  Otherwise the trinity phantom true wireless sets look somewhat promising.
 
Just keep in mind even with apt-x you won't quite match the quality of a wired connection from a decent source so keep your expectations reasonable.  I currently use a trinity mmcx lanyard with my SE425 at the gym and though FAR better than my freshebuds pro I wouldn't use it for critical listening. 
 
The new Fiio lanyard is due out soon, and it might be a good idea to wait and see how good that is.  On paper it looks like it could have reasonable good performance.

I understand that my iPhone 6 Plus is not an Apt-X capable source. Also, I'm not sure what a lanyard is. It seems to be some kind of cable? It seems that the SE425 is not a wireless IEM at all. Is it somehow possible to convert it to wireless using this 'lanyard'? I'm also not sure what this new product from Fiio is. Googling 'Fiio lanyard' comes up with nothing.
 
So, there isn't a high quality true wireless IEM apart from the Trinity Phantoms which aren't due till Feb 2017? I expect more like them are expected in the near future, maybe from major manufacturers?

 

[WhiteKnite]

Yes, basically you can convert detachable cable iems to wireless.  This is the fiio I was referring to: http://www.head-fi.org/t/817539/turn-your-detachable-cable-headphones-into-hifi-bluetooth-headphones-fiio-btc-mmcx 
 
Here is the trinity one I use: https://trinity-audio-engineering.myshopify.com/products/trinity-bluetooth-lanyard
 
Westone also makes one, but I'm not sure how they compare.  There are also a number of cheap, low quality ones on aliexpress or ebay.  Don't worry too much about not having apt-x.  It still won't give you audiophile quality BT streaming (at least not on the devices I've heard) but will just get you closer to a wired sound.