The EON is the name associated in the Comma.ai community to the devices that sits in your windshield and does all the calculations for LKA and ACC.
The EON is based on the Qualcom Snapdragon 821 mobile platform. Phones like OnePlus 3T or LeEco LePro3 have been used to create the FrEON (the free EON). You can find some instructions here. As for me, I opted to buy the EON directly from Comma.ai to support their efforts in this space.
If you chose to buy your EON already made, you can do so from Comma.ai store for $499 USD.
Also, as we run more and more processing on the EON, it gets hotter and hotter. Some of us have opted to replace the original fan (which is also noisy when you're inside of a Tesla) with super quiet Noctua fans. $15 from Amazon and soldering two wires and you're good to go! We might have to actually double that to two Noctua fans in the neat future.
Also, keeping the phone screen off helps keeping the temperature low. I know, in the beginning one wants to see those lines matching the lines in the video, but after a while you stop paying attention to the screen. And if you have the IC integration all the data is on IC anyway. So turn that screen off and you will see the temperature drop about 15F.
Code for power management of battery (only charging when below 60% and stopping the charge when it reaches 80%) have helped keep the battery temperature lower and hence the CPU cooler. And this is a free upgrade, as the code is already in my repo.