I've been using Bluetooth for the past few years, work fine for me. Every time this comes in, at least one member will chime in about lag, latency, or delay. If it exists, it can be more than a couple of milliseconds. Might notice it watching a video, but not an issue talking on the phone, or metal detecting. Bluetooth 4.0 came out last year, so you might snag what you need on the cheap, as they clear out the older versions. My transmitter is 2.1, and will probably get a 3.0 or higher, if I see a good deal.
Great thing about Bluetooth, vast assortment of headphones, earbuds, earpieces to choose from. Also receivers to plug in your favorited corded versions. Most digital wireless solutions offered here, you are stuck with the headphones married to the transmitter, and you can't simply replace one or the other, you have to replace the whole setup. I use a single earpiece, just like leaving one ear open, and aware of whats going on around me.