Best free EFIS for FlightBox?

Please provide the following information:

[ x ] FlightBox Kit
[  ] FlightBox Assembled (FB1X)
[  ] Generic Stratux

FlightBox / Stratux version: v1.0r1

FlightBox / Stratux build: 51989F

Radio Configuration:
[ x] Dual Band
[  ] Single Band - US / CA - 978 MHz UAT
[  ] Single Band - International - 1090-ES

GPS Configuration:
[x ] None - Using mobile device's GPS
[  ] Open Flight Solutions Remote GPS
[  ] Internal GPS Module (VK-172)
[  ] Other:

USB Power Source:
[  ] USB Battery: (Make / Model Here)
[x] Cigarette Lighter Adapter: 3 amp

USB Cable:
[x] 3' heavy gauge cable included with FlightBox
[  ] Other: (Make / Model / Description Here)

EFB Application name and version:

Please include a detailed description of your issue or question:

What free EFIS app would work with this AHRS upgrade?

On iOS you only have one completely free option, FltPlan Go. On Android you can use either FltPan Go or Avare. Chris Young, the creator of Stratux, has a fork of Avare that’s much easier to use than the original.