Personally, I think the technology just isn't there yet and there's a user interface design issue as much as there is a lack of software.

What could make a tablet come alive for me? First, a precise stylus technology like wacom or similar is a must. The only tablets I've ever found regular use for had this feature. I currently use my remarkable tablet the most, if you want to even call it a tablet. If I can't write on it, I think a tablet is pretty useless. It's clunky and hard to hold and move around with. But I regularly carry books or a pen and writing pad, etc.

Next up, the real breakaway technology would be some type of hybrid screen that can act as both an E-ink screen and something more conventional with back-lighting and color. Something good enough to watch a movie on.

Next, input technology on a tablet sucks. I think tablets should have physical buttons and multiple USB ports and things like that. Bluetooth can be done right, but it's so often done with such cheap hardware that the end result is just unusable, and it's not a real option. A better wireless connection standard could work, particularly one that specified hardware capabilities that were actually sufficient.

Finally, in terms of software, I think the real breakaway technology would be a really seamless and effortless cloud syncing where you never really have to leave one computing environment for another. If I'm reading something on my computer, and I realize its time to make dinner or something, I'd love to be able to just pick up my tablet and carry on where I left off without really having to do anything. Just turn on my tablet and it acts like a seamless extension of my desktop or something.

There's a LOT of technologic magic that would have to happen to make that work though! It may not ever be quite possible, and worse, it may not even be desirable for a broad user base! And none of the above really address the complete scope of user input issues. Keyboards are great. Most modern UI design is crap compared to old-school keyboard navigation. (Though I must once again give a shout-out to Microsoft's Office approach to this. No need to remember an impossilby long list of shortcuts. One press of the alt key and your path is illuminated before you. Whoever designed that concept deserves a medal.)

I think a lightweight 2 in 1 workstation concept with a stylus is probably just a superior idea all around.

The ultimate, yet-to-be-realized killer app of a tablet would be to act as large drawing, editing, and writing surface in augmented reality -- and a cutaway-plane viewer.

Currently, it's mostly used (1) to consume content, (2) as a large touchscreen input device for skeuomorphic apps, and (3) as a drawing tablet.

There’s a whole universe of control surfaces beyond QWERTY keyboards and mice. The iPad is a versatile, cheap, and most importantly mobile substitute/companion for a wide range of professional equipment consoles.

For me it’s digital sound boards.

The killer apps for tablets arrived years ago! Entertaining children, low-end point of sale devices, and watching streaming videos.

The killer apps for tablets are art (like Procreate) and being able to use the tablet while lying down on the couch or on a bed.

Staffpad. https://www.staffpad.net/

But make it actually work.

Applications that require handwritten input is what the tablets should all be stretching towards.

I can fat finger things on my phone. I can type on my laptop.

But I can't write on anything.

I still want the thing that was supposed to happen a while ago. The phone that is the tablet that is the desktop. You just plug it in to the appropriate form factor, but the computing device is the same.

a few devices/companies have tried this (not Apple obviously):

Motorola Atrix: https://en.wikipedia.org/wiki/Motorola_Atrix_4G#Accessories

Microsft Display Dock (Windows Continuum): https://en.wikipedia.org/wiki/Microsoft_Display_Dock https://www.microsoft.com/en-ca/windows/continuum

NexDock: https://nexdock.com/

Samsung DeX: https://en.wikipedia.org/wiki/Samsung_DeX

Apparently Android 10 has a desktop mode as well

Why do you want this, though? File syncing is a largely solved problem, and the difference between a "laptop-shaped thing that you can dock your phone with" and "a fully functional laptop" is like $20-$40, at least to be on par with the speed of a phone powering a laptop shell? Why not just spend a little extra and have a full computer?

There are a few reasons I want this outside of file syncing.

1) It somewhat feels like it could be less wasteful. It may only be on the appearance level, but I end up with a new phone about every 2 years, a new computer about every 3, a new monitor...much less often. If my phone was a smart client for these other input devices, I feel like I would be upgrading my phone about the same, but wouldn't be upgrading a laptop as often.

2) It "feels" like the same device. Though I have file sharing, I don't have desktop sharing. The file I stuck on my desktop on my laptop isn't in the same space on my phone. It feels like they are synced, rather than just being my workspace.

3) I have to duplicate my apps on each device, and that is not always possible, so I end up with a comparable app, or having to switch devices. This is becoming less common, but still, do I need to have multiple versions of the same software on each different device and different OS?

4) Notifications everywhere. When I'm being summoned on multiple messaging apps, I'm getting notifications on at least 3 devices! Yes, I could turn notifications off, but obviously, I need some notifications. If I had only one device, acting as the smart hub to other input devices, in theory, it would know which device I'm active on, and just ring that.

At the same time, we work a bunch with graphics, so I don't think I'm getting decent developer capable graphics card in a mobile device anytime soon, but I think other users could move to this sort of paradigm fairly easily.

Pen-based note taking or drawing already seems to be a (small) killer-app. I've heard several people say they bought a Surface or an iPad Pro purely for one of those two tasks.

The killer app for the iPad is to be paired with Zoom as a sketching device for meetings, a shared whiteboard that actually works and you can write rapidly and accurately on.

For me, the pencil is the killer app for my ipad. It's turned a nice to have gadget into an essential for getting anything done.

I've always wanted live monitoring from SLR/Nice Camera straight to iPad for focus/composition monitor. There are hacks to get there now, but they all suck and cost a lot.