I’ve made a script that will return the top ten power levels along with their respective frequencies from the rtl_power output. It takes less than a second to run, according to the creator’s website the rtl_power utility cannot run faster than once every second. Since the script runs faster than the rtl_power can complete its next scan it could be used while the next scan is being run without slowing down how fast the scans can be run.
I found available images for both raspberry pi and something called BeagleBone black that already have all the gnuradio and rtl-sdr stuff installed on them. Links: http://www.kd0cq.com/2014/08/packed-full-beaglebone-black-img-file-rtl-sdr-gnuradio-gqrx-lots-more-on-ubuntu-14-04/ and http://garethhayes.net/gnu-radio-for-raspberry-pi/ . Both creators say that the rtl-sdr and gnuradio tools I’d need are already installed on their images and that 8gb SD cards are necessary.
For antennas: I realized the USRP antennas are intended for use in the GSM frequency ranges. With a SMA female to MCX male adapter like this one, http://www.amazon.com/coaxial-cable-assembly-female-right/dp/B00CP17WMG , it could be used with the RTL-SDR. I could still try to build my own antenna; I’d need some copper wire and a coax cable, but I doubt I’d make a better one than the one that the USRP was working with.
I also tried to learn more FFT stuff. I don’t think I really understand it yet so I’ll keep looking.