Android

Headphone jack. I've used multiple LG phones before, currently using the LG V60 and seems like Sony is the only way to go in the future, unfortunately.

More phones like the Fairphone/Framework Laptop. Easy to repair and upgrade in a modular manner, as well as install what ever OS I choose.

IR emitter . Super handy wen you use old stuf like me like VHS dvd combo crt ect .

An ir blaster, great as a universal remote

Slide out physical keyboard, notification LEDs or some form of cool lights, a dedicated camera shutter button, and a scroll wheel / touch pad like what used to be on the blackberry or like the LG KE970 I really liked that.

I really miss notification LED's though, always on display is good, but a little light is going to use far less battery and be immediately apparent from across the room by the colour what app the notification came from is.

edit : formatting

Plastic back and a removable/user replaceable battery.

Yeah yeah I know it "feels cheap" but honestly I LIKED when phones were made of more plastic. Now they're heavier and both sides are breakable. Like, the metal backs were fine, but apparently metal backs suck for NFC and wireless charging so instead of giving us some classy Nokia Lumia style plastic they went with glass backs.

Also I keep my phone in a case because otherwise the back is so smooth it shoots off the couch if someone walks across my apartment. It's legit only in the case to add some friction.

This is going to be such a stretch and I doubt this would ever happen, but if you could get a decently sized camera sensor on the back of a phone and a mirror less style lens mount...I would sell my DLSR in a heartbeat.

3D Screen Pico Projector HDMI out Notification LED Removable battery

The first smartphone I owned was the Lobster 700TV, Which as the name suggests had a digital TV receiver built in. The screen was too small to be practical, but I've always liked quirky features like that

I liked the physical toggle for silent mode on iPhones. Flip/slide-out keyboards were also kinda cool

As far as apps though... I really loved having a good programmable remote app on devices with an IR transceiver. The best one was actually on Palm of all things, and you could add custom icons to a layout and then record inputs from your actual remotes to replay.

A microsd card slot and a headphone jack

Officially supported rooting! Makes this less complicated.

Modular everything. I really wanted Project Ara to come to market.

IR Blaster, Headphonejack, SD Card Slot, removable battery

Today my wish is for an internal pihole instance running on the device.

Max 4 inch screen, IR blaster, physical keyboard with speed dial settings for buttons, form factor like the Xperia x10 mini pro, headphone jack, cameraless, LED with customisable lights for different notifications, bonus - built in projector, satellite phone capability,

Native Bluetooth GPS support. I do mapping for OpenStreetMap a lot and the built in GPS modules are just too bad for that. Currently I have to use an app to get my Bluetooth GPS connected. But sometimes this app fails and the built in GPS takes over and ruins my logs.

Better system font/typeface selection and a way to install new ones. I know it's a petty gripe, but the default android options are few and terrible.

I'm on a Fold 4 now and I do love the novelty/oddity aspect of having a folding tablet.

But I would love to see the return of IR blasters on most phones and sliding phones for physical keyboards.

Really would love a dedicated camera button that acts as a soft shutter release. Or a button in that position that's programmable.

Phone upgrades.
Battery.. Non lithuim. Flexible and new. []
Flexible screen. Wrist strap or just flexible. []
Fitness/health capabilities. []
Usb 3.1 reversible.. Proper specs [x]
Wireless charging. Using new WiFi microwave to charge phone without mat. Wattup []
Better nfc/Google pay [x]
Smaller screen oled,s than 5.5 []
Better speakers none conduction or ceramic
Encryption []
Bezelless. Screen to screen hole cut out. 2018 []
Solar panel in screen. Sapphire glass. Smudge and germ

This list was created a few years ago.

Some things have been implemented but not all.

Slide out controller, like the Xperia Play. I've gotten super into (at least the idea of) SBC handheld gaming, and there's just nothing quite like the Xperia Play now. Sure, there's bluetooth controllers, but I'm not a big fan of bluetooth, and the majority of the bluetooth controllers make portability a pain rather than it being a sleek package.

Keyboard and not every phone looks like a black slab

Ability to use the screen as a display through the USB port so I can debug a lot of my systems at home without needing to carry a monitor around.

Hackability

I enjoyed the squeeze to activate assistant on Pixel 2 XL..just felt right. I even configured it to activate flashlight when I needed a quick light.

Does the alert slider counts as a niche feature? Very few brands provides this.

i'm certain this is going to be a just me thing but i'm a nostalgic fool and would love a notch in the casing to put a lanyard/phone strap. that, and a physical keyboard. if you could get modern android and a good camera in the form factor of the original motorola razr i'd be so happy lol

I just want a new Droid with a slide-out keyboard

I've had every one of them until the Droid 4 and they never released a new one

I loved the IR Blaster on my old Galaxy S4, was really fun to mess with the TV's in public places with it sometimes and was also pretty useful at home as well!

true background process management and battery

Headphone jack. 5in or less screen size.

Foldable display - They are still way too expensive!

Metal case - I just loved the heavy Samsung Omnia metal case. It made it unbreakable and grippy!

duck duck go tracker blocking that doesn't use vpn technology