I think this could even be almost with a few small changes. I think there is room for a new class of device in between smartphones and fixed function machines like TV remotes.

If I bought an OSHW product and it shipped with this as the controller, or I saw one of these just hanging out running an irrigation system, I'd say "Yep, they sure did an awesome design there.

I would ditch the SD card as part of the BOM. I don't trust that $2 SD card for anything but read only root operation. Lots of people would rather use a SanDisk they already have, so I'd say the cheap card should be an optional addon.

With the money saved from that, and maybe by just bumping up the price a tiny bit, could you tack WiFi/BT?

This sounds slightly insane, but what if you slapped an ESP32 module on there?

Not only could it serve as a WiFi and Bluetooth interface, but the power draw can be microscopic.

You could have the option to have it always running. That means it could be the real time clock.

RTCs are needed more and more for various security related things, and are very important for data logging.

Instead of breaking out GPIO for the "shitty ad-on" connector, break out ESP32 GPIO.

Now that add-on can run IN LOW POWER MODE!!! You could make an incredibly low power thing that logs to RAM, and wakes up once a day to 4G upload it!

It could also serve as the battery level ADC monitor if you don't already have one.

It could serve as the USB device for the C port, so you could plug it in to a a host machine AND have the spare USB-A port.

It would also let you really deeply control and test network access. Since you can write your own ESP firmware, and it has GPIO, potentially you can implement your own IP-over-LoRa hackery with addon modules or something, that works transparently.

It's large RAM could also be exposed as a filesystem for tiny frequently updated things, that only need to be semi-persistent.

Plus, you could give it a debugging firmware and use it as a USB to serial interface for debugging. The whole platform kind of becomes software defined!!

You might need some kind of recovery jumper in case bad ESP firmware told the main processor to shut off, preventing you from fixing it. But that could just be a DIP switch to disable the ESP, which would also act as an RF kill.

Going eeeevvven fuurrrtherrr*, that NiMH is probably the second biggest weakness here.

I think there would be more demand if you swap it for an 18650 or lithium AA, even if it cost more.

If you look around, a lot of people really love that form factor. You could save a bit of money by just letting people use their own 18650.

Or, even better, you could use a 2.4V LTO battery. These are $3.30 in QTY10 on AliExpress. They can be float charged. They have a linear voltage curve. Incredibly safe, and they can last 7000 to 20k cycles.

Set your step down regulator for the float voltage and you are good to go if it's accurate enough. Use an IO pin that can turn it off and you can terminate for extra life.

With a simple dumb charging regime, you will have no oddities when running right off a solar panel through a 12v to USB converter.

Now you have the perfect offgrid tech tool!

If the extension interface has a good mechanical connection(Like a screw) and 3D-printable addon modules, a lot of standalone devices could go away.

OBD scan tool? Multimeter? Geiger counter? Nope, just sell these in a kit with a preattached module.

For niche hardware it might actually be cheaper to rebrand these than to do your own interface, and these are way more flexible.

Lastly, the ESP32 can handle audio, and audible alerts are important.

But beyond that, walkie talkies EPICALLY SUCK. It would add cost, but the thing could almost totally replace FRS radios, and have 10x the battery life and as much range as you want with Wi-Fi mesh, with just a tiny speaker and mic, or even without one, just using bluetooth.

Plus, sound is pretty essential for use in a game console.

Currently, there are basically no devices in this class since things like the Zipit Z2 went away. So I am super excited to see how this goes!!

I already have some ideas for a menu system that could make this usable for non-hackers, without going to a full GUI.