Pocketable / clipable essential accessory for modern smartphones
Apple ditched the headphone jack four years ago, and many other phone manufacturers have followed suit, but my wired IEMs and headphones are still a part of my mobile life, and the ES100 offers not only wireless connectivity with plenty of codec support including aptX and LDAC (although my iPhone only uses AAC and SBC, admittedly), but also includes a mobile app with a decent 10-band EQ. I'm one rarely to use EQ because I use streaming services (Tidal, Spotify, Apple Music) and there is no system-wide EQ in iOS, but I've found with the app and my ES100 that even I will play a bit with EQ for IEMs that benefit from it (*cough* Shouer Tape *cough*), and this is very convenient.
Generally, I'm more of an over-ear headphone kind of guy, but at the gym, when I really want to hear more than I can get from wireless earphones like my RHA MA750, the ES100 is my goto with several IEMs to choose from that I carry with me in my workout bag for variety -- Shuoer Tape, oBravo Cupid, PSB M4U, among others -- and for some of these, I really need the ES100 to drive them as they do not really get adequate power from a phone headphone jack or the standard Apple dongle. In the case of the Tape and Cupid, I'm getting more power from the 2.5mm balanced output, at that.
Some minor quibbles with this unit: build is "meh", with tiny little buttons and it's frankly cheap feeling -- and the clip on the first one I had (MK1) actually broke, although the clip on this MK2 I bought from Drop has been fine so far. But, the bottom line for me is this has made me really not think a whole lot about losing the headphone jack -- I get better amplification from this little ES100 than the headphone jack ever gave me, and more versatility, too.