Thanks for all the great ideas.
The Flysight is exactly what I'm looking for but I haven't been able to find it for sale anywhere. Maybe still preproduction? I'm going to try the portable TV idea to get by until it's available.
edit..... I see it's on Indiegogo.
Be careful about that Flysight HD900. There are absolutely no reviews anywhere online, but tons of ad pages with no comments whatsoever. I actually saw it in a shop here where I live, so I bought it with some reluctance, drawn in by the HDMI options like you.
But I'm not totally thrilled and still deciding if its worth keeping. Depending on where you order from its probably between USD $300-$400. It's running Android 4.4.2, already fairly obsolete with Android OS 7 already touching the new Nexus models. It's a Chinese company Android tablet, so don't expect too many updates if any. Flysight makes fpv goggles and I guess these are fairly popular, but they don't have android tablet experience and this thing is not very standard so you can expect some issues.
First problem I found out was that lots of apps aren't compatible, either due to the custom hardware or the older OS version, I don't know. Yes you can install DJI Go, but both Litchi and Ultimate Flight say "not compatible with this version". Lots of other apps report incompatible from the Play store. I was able to download the apk files and manually install them after all, but not everything will work that way. Chrome itself won't install even manually with the apk. So I installed Firefox, but it crashes routinely. So the default web browser is the only one that will work reliably.
Next problem is the HDMI input. It works taking a signal from my laptop, but connecting my Sony mirrorless reports on the screen "not support formate" (spelled just like that). If it won't work with HDMI source from Sony's flagship mirrorless camera, then I don't know what cameras would.
It's also heavy. It comes with a metal replacement of the tablet holder part on the dji rc. Thats pretty nice, but even then you just cant tighten the holder enough to keep it from falling backwards from the sheer weight of this tablet.
The Flysight web site actually has a page with software downloads, including a firmware update from just about a week ago. I thought this might fix the HDMI input to work with my camera signal. Instructions are to format an SD card as FAT32 and put the firmware on the root and boot with a button combination. I did this properly but a message always reads "fatload failed" and doesnt begin any update.
There is NO support available. Looking around the Flysight web site there are a few contact email addresses to be found, only for sales. I emailed all of them I could find asking where to get support. Nobody responded. There is live chat for sales. Nobody replies in the chat window. One person did. When I asked if any support is available the chat ended.
The screen is really nice at 2k resolution and yes it is bright. It also comes with a sunshade but its bright enough you probably dont need it. Otherwise the specs are not incredibly impressive, a 2014 era Samsung Exynos 5260, which is a mid range hexacore cpu running at 1.7 GHz. 2 GB RAM with 16 GB storage and SD card slot up to 64 GB compatible.
In the field the display is ok but its not powerful enough to run Litchi properly and it does keep trying to fall backwards in the holder arm, so its distracting to keep it upright due to the weight. And sound is almost non-existent. You have to hold it flat against your ear to really hear anything in ordinary ambient environments, so don't expect to hear audio announcements and warnings while flying.
I write this here because I can find NO reviews whatsoever on this tablet, but tons of advertisement pages all over the place, so maybe it helps someone else who is thinking about it like I was. I am still deciding to keep it or try to return it. For the price I paid, it isn't a bad deal and with the HDMI out, if I had a set of FPV goggles I could probably use the HDMI out port instead of purchasing the HDMI add-on from DJI. But from everything I hear, I think the Nvidia Shield K1 would provide the same option in a much better performing, as well as better supported device, running a modern version of the OS and compatible with all current apps in the Play store.
If you have any questions about it you can ask me, since nobody from Flysight provides any answers.
