No, but multiple GPS' can suffer simultaneous, independent failures. The Garmin GA35 active antenna has a well-known failure mode that causes it to oscillate in the GPS band, thus effectively jamming any oth nearby GPS units until you turn off the GPS using the offending GA35.
My KLN-90B does not provide terrain warning, nor any ASI functions. I think you misunderstand exactly what you can get. I do get Synthetic Vision with my SkyView system, but that is not TSO'd and this is advisory only. 747's and their ilk are provided with automated position source monitoring and will flag an EICAS/ECAM message if there's a disagreement. We don't have that.
That can, and have been, jammed simultaneously by a failed antenna. If you have a second TSO'd GPS, carry on as normal using that as your primary. If you only now have an EFB, you're down to VFR map-to-ground.
I use my KLN for position checks primarily, as it is TSO'd for Area Nav, IAW the AIP. It's only when low level I use the map.
No, no no. Please do not be lulled into this false sense of security about 'real time' weather, the BOM overlays while pretty good, can be delayed by 10-15 minutes and this has been proven to have caused accidents overseas before, with pilots relying on NEXRAD returns to avoid weather and unintentionally flying into a rapidly developing storm because it 'looked clear' on the EFB.
Because while it does indeed do most of those things, it also has some very significant limitations that you need to be aware of, and a brand-spanking new pilot is not likely to fully grasp them until he has had time to understand that concept, something unlikely in the early stages of flying.Don't get me wrong, I am all for sole-means GPS Nav for VFR vs DR, but and it is a huge BUT, a pilot need to understand the limitations of the system he is using in order to keep themselves and their passengers safe. Using OzR/AvPlan for maps only during a PPL test, I have no problem with. If the ATO simulates a failure and you have a backup EFB, no problems, continue using that. But a lot of the functionality built into EFB's can provide a false sense of security that needs to be understood.