If you are looking to make an embedded focused VM, obviously ARM is the most useful target to run on.
The two main ideas were to be different implementation for large machines (ErlangRT) or to be small (E4VM and gluonvm1).
BEAM has been in use for over 20 years in telephone systems running on insanely old and bizarre hardware. Is there a platform you have in mind besides ARM?
edit: it's a work in progress, but it's a start. Looks like the author is actively working on it.
For ErlangRT the original idea was to reproduce some subset of existing Erlang/OTP emulator features and then optimize from there. It resembles Erlang/OTP data formats and data structures, so it would begin at 1:1 ratio or maybe a little worse like 1.1:1 or something because Rust incurs some costs for compound types where for C it was enough to have an integer.
Author is here.
We have no idea how this blog draft escaped into HN, but here it is a few years too late. The Gluon project https://github.com/kvakvs/gluonvm1 isn't live anymore, it was using C++ and it was stopped a couple years ago giving way to other experiments ( https://github.com/kvakvs/E4VM ) and finally to ErlangRT mentioned below https://github.com/kvakvs/ErlangRT
My talk with me explaining the whole thing on EUC 2017 (Stockholm) is here https://youtu.be/6NUPormxgw8?list=PLWbHc_FXPo2jAL3fm0YfN3nFV...
The new ErlangRT project in Rust is much more recent; clean strictly typed code with some 'unsafe'ties and a good PoC progress. But it also was stopped because the amount of work to do in it quickly grows but my free time doesn't grow at all.
This increased interest might actually make me rethink my priorities and look at it again.