The Embedded Systems Language is described by the upstream project as "a typed compiled language with features that allow the programmer to dictate the concrete representation of data values. This distinguishes it from languages which implement only “abstract” types or types whose representation is architecture-dependent. The programmer can dictate the details of data representation, including such things as “endian-ness” and the exact placement and packing of bits. These are necessary in dealing with external representations of data layout, e.g., communication protocols or device registers. Procedures can return multiple values."
On the ESL project's Google Code page is the source that compiles against LLVM for Linux and OS X systems. There's also the programming language documentation, but it's said to be incomplete right now.
Do we need yet another programming language?