SkyView's USB is a standard USB port, so it can deliver standard USB power.
However, the specific "USB" devices you named - iPhone and iPad, are not quite standard USB devices when it comes to power. Apple played a bit loose with the max power that the iPhone and especially the iPad pull from USB.
For example, Apple's "USB" charger for the iPad provides 10 watts. Given that USB supplies 5V, that means that the iPad needs 2A to charge - that's more 4x standard USB power.
SkyView is a multi-thousand dollar piece of flight critical avionics. Putting a load on the USB port makes it work harder and get hotter. It's unlikely, but possible that a USB device could act up and make SkyView shut down.
We really suggest a 12V to USB power converter in your plane if you want to charge your iPad in flight (because of that extra power required for the iPad, make sure the 12V to USB converter specifically says that it'll charge an iPad.
It's cheap insurance. If you need to use SkyView once in a while or in an emergency, then it will work fine.
