There is currently no limitation on how many devices a subscription can be used on. If you just made your purchase, you may need to log out and log in again on the device you made the purchase on, so that the subscription gets registered with our servers.
I've seen accessories where they actually sell Antennas that you put on top of your Vehicle so you can have warm Fingers by Flying your drone in Cold Temps from the Comfort of your Car!! lol For instance here's one... http://amzn.to/2mSAsUT
One subscription works across all devices, but you need to create a UAVForecast account and log into it from all your devices in order for this to work, as explained in the app next to the purchase button. Apple's non-renewing subscriptions do not automatically transfer to other devices and refreshing purchases on another device will not automatically activate your subscription on that device too. You need a UAVForecast account because the subscription information has to be uploaded to our servers for this to work.
When you purchase a subscription on iOS, you need to create a UAVForecast account, otherwise if you upgrade your device or lose your settings, your subscription may be lost. This is explained after making the purchase. If you did not do so, or if your subscription should be valid but not showing correctly, please contact email@example.com and let us know your device ID(s) (from the Settings tab), and include a copy of your iTunes receipt(s), and we'll try to fix it for you. Thanks!
It is very rare for UAV Forecast to show only 6 satellites in the sky. What is your location? Can you send me a screenshot which includes your location and shows the 6 satellites? The data is derived from regularly updated ephemeris data of the orbits of GPS satellites and is very reliable. However, a lot depends on how much of the sky you can see from your location. If you are surrounded by tall buildings, you are not going to be able to establish direct line-of-sight to all the satellites that are above the horizon. This is the purpose of the "GPS Elevation Mask" setting in the app and on the site. If the app is showing only 6 satellites available, it is possible you are using too high a value for this GPS Elevation Mask. Ideally, you'd set it to the average angle of the buildings around you relative to the horizon, i.e. when surrounded by tall buildings, set it to 20 or 30 degrees; when in an open field with a full view of the sky, set it to 0 or 5 degrees.