It is finally available! I predicted it about a year ago, when I first ordered my tablet, and thought about writing it myself, and asked for help. I am glad there are more ambitious people out there, because they get it done. My Android development skills aren't there yet either. I am working on an app that will use maps, but haven't got to that part yet.
The app is $1.50 in the PlayStore, called ADS-B on USB SDR RTL (beta) it shows up in apps called "USB ADSB..." on the tablet. The USB dongles are really only about $15-20 US, plus shipping. You will probably need an OTG cable or adapter for a phone or tablet. (The OTG cable allows attaching USB client devices like mice and keyboards to a phone or tablet). Really the cost may approach $50 plus a tablet.
The app shows promise, and really looks nice. It starts the map centered on Lakeland Florida, so it needs to be adjusted to where you are. The maps can be sectional, WAC, IFR, and street maps, and can be selected from a menu. The pinch to zoom works, but the menu allows zooming, along with buttons in the upper corners.
When the app comes up, it displays all the available devices, selecting the available device starts the app. The top part shows the map, the bottom part shows a list of the aircraft that the software has heard recently (can be adjusted in startup menu, defaults to 60 seconds).
It appears to be listening for 1090MHz Mode S with Extended Squitter (ES) transponders. 1090ES is the world wide standard. GA in the US will probably focus mostly on the 978MHz UAT devices, since there is more bandwidth available to those devices. See UAT or 1090ES in my other blog).
The developer says it will have weather eventually. Weather alone would make this app worth while, but the aircraft positions is a huge benefit. "Mounting" a tablet in an aircraft isn't hard, and there are a few adapters to make it easy.
This doesn't completely compete with the Garmin GDL-39, and their Pilot app, but it will give you the chance to see what is possible, and the benefits to having ADS/B service.
I had trouble using it. The SDR dongle is very sensitive to the antenna chosen. I found a link to a site were there are extensive design and testing of antennas especially for ADS-B reception:
I chose the simple 1/4 wave dipole and was able to get some reception. I didn't want a large antenna, nor an amplified one. I want to be able to use this portable in rental aircraft and such. It did seem if I got the SDR farther away from the tablet, it worked better. I used a USB extender to do that.
The battery life doesn't seem to be negatively affected running the SDR dongle, the screen still eats most of the battery. Someone suggested a split OTG cable, so it could be connected to power while running the SDR dongle. That is a great idea.
I can't say this will save a life, or replace TCAS for alerting, but it could help someone get the big picture when ATC calls out traffic.
If everyone only does ADS-B in, it looses some of the benefit. The future will require us to use ADS-B out as well, then everyone should be on the same level.