The company Giiker came up with the first ever Bluetooth cube sometimes in 2018. Currently there are many different versions you can buy on eBay, Aliexpress etc. and some selected stores around the world. All versions are supported by CubeSmith, but I recommend buying the latest versions (i3S, i3SE or i3S Light). One cube is enough for most of the effects, however, the real killer is the cube cloning effect, for which you will need 2 of the bluetooth cubes.
Xiaomi also came out with a bluetooth cube, called the "Xiaomi Mijia Magic Cube". Currently this model is my favourite of all available bluetooth cubes, see details below.
Also there are bluetooth cubes from GAN and Rubik's, and of course CubeSmith supports most of them.
As I mentioned above, currently the Xiaomi Mijia Magic Cube is my favourite bluetooth cube. This cube has a replacable button battery (1632) therefore it has no charging holes. The body of the cube is black matte plastic, and the stickers have nice pale colors. You can re-sticker it if you want a more authentic look. The cube goes to standby after 15 minutes if not connected, but stays connected forever once you use it. I recommend buying it on Banggood or Aliexpress, usually it costs around $20 - $30 but the price is slowly going up. I recommend ordering 2 cubes at once. :-)
There are many versions of the Giiker bluetooth cube, and all of them are supported by CubeSmith.
Giiker cubes usually sell for around $40 - $60 worldwide. Unfortunately the 2018-2019 models tend to have an out-of-sync problem after some months of usage, but maybe this bug is corrected in the 2021 Light model.
The more expensive GAN 356i (v1, v2 and v3) has a gyroscope, so we can tell which side is facing up. The cheaper GAN 356i Play lacks the motion sensor, but it's battery life is significantly better. The GAN 356i Carry and the GAN Monster GO MG3 Ai are powered by a button battery, so they need no charging. GAN cubes are usually available in stickered and stickerless versions. The cubes are really light, magnetic (easy to turn) and they don't beep when connecting/disconnecting. However, if you play with them while not connected to the app, they loose sync and you'll need to manually solve them (and do a RESET in the app). You can buy theese currently marketed cubes directly from GAN:
The Rubik's Connected has a rechargable battery, doesn't make weird noises when turned, doesn't beep when connecting or disconnecting. Always ready, no need to wake it up. It only needs restickering, as the white center has the Rubik's logo, and the yellow center has the charging holes. After restickered, the cube can be charged after temporarily removing the plastic cover of the yellow center. The price of the cube is quite high, but I think it's worth buying.
The Rubik's GoCube-X has a CR-1225 button battery (no charging needed), doesn't make weird noises when turned, doesn't beep when connecting or disconnecting. Always ready, no need to wake it up. It only needs restickering, as the white center has the Rubik's logo, and the yellow center has the charging holes. After restickered, the cube can be charged after temporarily removing the plastic cover of the yellow center. The price of the cube is quite high, but I think it's worth buying.