Alesis was the first manufacturer to officially call their MIDI handheld keyboard, the Alesis Vortex, a "keytar" in 2012 and I bought one as soon as it came out. This is a fun MIDI keyboard that allows me to stand where I want when I jam live. The price is very attractive and they even make a wireless one for anyone that wants even more flexibility. For my purposes, the Vortex's 6.5 lbs. and full-sized keys make this a better keytar solution for my use compared to more expensive ones.
I bought this because I liked the look of it and convinced myself I would use it a lot. I don't but I still like it, it's straightforward to set up and use out of the box but more complex if you want to do more than use one module with it, I have three modules, you can do lots of clever splits and so on with it, but the most I've done it to be able to change midi channel with a button push and set a specific sound to be triggered by a pad. So I've not done a lot.