Same here. I remember hearing about their SD-form-factor product, like, 5 or 10 years ago. Then cheap wireless microcontrollers like the ESP8266 came onto the market and made them irrelevant.
They had that SD to WiFi card which was interesting to have say a non connected camera send directly photos to a server through an access point. An ESP8266 or ESP32 might probably accomplish the same by implementing SD card emulation on some of its GPIOs. But the form factor would be much less convenient.
Are you sure that was an Electric Imp product? I'm pretty sure those were from other companies, like Eye-Fi (and later others).
You're right, thanks for pointing out. They made a SD looking MCU board with WiFi, but that didn't work as SD emulator they just used the connector because it was cheap and ubiquitous.
They moved out of their SD card format and into the software stack a few years ago. With Twilio’s recent launch of their esim product for IoT it seems like they are building up a full stack IoT platform.