Electrical Engineering has a fairly active Android tag.
As with any other site on SE, it's important to do some background research before posting your question. For example, being able to refer to specifics on the datasheets (usually available as PDFs from the chip manufacturers) is important for any type of troubleshooting, and is where the more experienced users will refer you to if you haven't referenced the documentation already.
As mentioned in the comments:
Right now, adding a GPS transmitter/receiver to my $20 tablet, possibly also adding more memory.
As an addendum regarding the above, "modifications" in this case should be changes to the actual circuitry and not consumer-grade add-ons for the platform. As in all cases, an inquiry on the site's Meta is the right way to go if the tour/help center is not definitive.