I have been creating an Espruino environment for the T-watch. You can see the results in the video below:
Bangle Apps can be ported fairly easily. The reprogramming required is to adapt the Bangle button controls to the touch screen. You can see my Multiclock app and @fredericrous 's excellent calculator in the video.
This was the biggest headache. I implemented access to the ESP32's light sleep, however, initially, the current consumption during sleep was 20ma. I nearly gave up at that point but eventually discovered that the ESP32 Espruino port initialises all GPIO pins with pullups. When I removed this initialisation, the sleep current dropped to 4ma. The T-watch has an AXP202 power management chip and by reducing the CPU supply voltage to 2.7V, the sleep current is now 2.5ma. The battery is nominally 380mah and probably more realistically around 300mah giving around 5 days standby power - not amazing compared to the Bangle but at least useable.
The active power consumption is around 90ma - again not great when compared to the Bangle, however the screen is brighter even at 30% of maximum brightness. To get to 90ma, I have removed the BLUETOOTH component which consumes around 40ma.
The T-watch has a 240*240 1.54ins screen driven by an ST7789V driver - the same chip as the Bangle, however the interface is SPI not 8-bit parallel. Thanks to @MaBe ‘s lcd_unbuf_spi module with recent performance enhancements, graphics are not as fast as the Bangle but are not unusably slow. The T-Watch has SPIRAM and consequently has 20,000 vars versus 2200 on the Bangle. This means you can freely use large ArrayBuffers and drawImage to reduce screen flicker - the analogue clock in the video uses a 200 x 240 2-bit buffer.
The T-watch has very few peripherals compared with the Bangle - speaker, vibration motor, infra-red receiver and accelerometer with in-built step counter (ASIC). It does however have wifi which I plan to look at next. The software is all on Github here but completely undocumented at the moment.
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