The MSP430 is just the chip I happen to use at work, if you’re not convinced you could try looking for an actual ultra low power chip, I found the STM32U0 at 70uA/MHz and the STM32U5 at 16uA/MHz in the first result.
Even ignoring selecting a more efficient micro, a smattering of tiny ceramic caps will buy you a few hundred microjoules for bursts. If you’re already operating at 2V you can get a 6V rated 100uF cap in a 1210 package - and that’s after considering the capacitance drop with DC biasing. Each one of those would buy you 200 microjoules, even just one ought to be plenty to wake up for a few tens of milliseconds every second to get a reading from some onboard peripheral (as an example) then go to sleep again.
For sure, you’re not going to be doing any heavy lifting and external peripherals could be tricky, but there are certainly embedded sensor use cases where this could be sufficient.
Not really. While working at the OS-level can typically require ‘unsafe’ operations a core tenet of writing Rust is making safe abstractions around unsafe operations. Rust’s ‘unsafe’ mode doesn’t disable all safety checks either - there are still many invariants that the Rust compiler enforces that a C compiler won’t, even in an ‘unsafe’ block.
And even ignoring all of that, if 10% of the code needs to be written in Rust’s ‘unsafe’ mode that means the other 90% is automatically error-checked for you, compared with 0% if you’re writing C.