You'll notice that we've setup a new development forum. The target audience of this is those Karoo users who want to take their Karoo beyond what Hammerhead intend, and exploit the fact that it runs Android and so modify it in various ways, install other apps, etc.
We've already put some warning notices in place on that forum but I'll repeat those warnings here. Whilst you might find it interesting to read what others are doing, anything that you choose to carry out as detailed in that forum is at your own risk. You really need to understand what you are doing if you start to diverge from the HH path, because you could easily brick your Karoo (turn it into a paperweight that doesn't even turn on), or end up with a device that HH won't support with no way to put it back to normal. Some people have extensive experience with Android and know what the limits are, but it's easy to think that it's safe to try something only to find out that you don't know how to undo it. So please take care.