The Banana M2 was mentioned here before as a Raspberry Pi Zero Clone, sharing the same Footprint and ports as the Raspberry Pi 0W. For it's size, it is everything a Raspberry Pi 0W except for its price. The R-Pi 0 is still sold at $5 and the R-Pi 0W is currently at $10. The Banana M2? Under $25. What do you get for the extra $15? A Quad Core CPU that can go up to 1.8GHz with Overclocking, 1.2GHz without. Everything else is about equal: 512MB RAM, 1 USB Port, 1 Micro HDMI, 1 Camera Port, 1 SD Card slot 1 USB-OTC (for Power In) all in a board about the size of your finger - the same foot print as the Raspberry Pi 0/0w.
 
Slated to be released in the fall, a new player has stepped onto the field of SBCs, named Redxa. Like Banana Pi, Orange Pi and all the others, they run some form of ARM based Linux and/or Android (which is Google's version of Linux). They are also trying to make their board footprint compatible with other Raspberry Pi systems. One of their soon to be released board is the Redxa Zero. It has the same footprint and ports of the Raspberry Pi 0/0w.
 
The only differences to the Radxa Zero are as follows:
- RAM: 1GB, 2GB, or 4GB.
- EMMC FlashRAM: 4GB, 8GB, 16GB, 32GB, 64GB or 128GB; bootable from the FlashRAM once the OS is burned in.
- Quad Core ARM A58, same used in the raspberry Pi 4.
- Mali 381G(?) Graphics Chip, as used on many ARM Based SBCs.
 
Everything else is like the Banana Pi and Raspberry Pi in terms of ports; except the camera port is missing (like on the Original Raspberry Pi 0 v1.2, the more popular Raspberry Pi 0 v1.3 and 0W has a camera port as does the Banana Pi M2).
 
Price on the Redxa Zero (and the other Redxa board) are unknown. They have released a few to a couple of Youtubers for review: containing 1Gb of RAM, and 16GB of FlashRAM with Android 1.9(?) already burned on it. Reviews are favorable as to what it can do, but they fear the price as the unit is yet to be released and currently unknown.
 
One of the few videos I seen which is more technical that the others is here: https://www.youtube.com/watch?v=huAKEbyPcBc