Is there some one that have manage to connect to a M-Bus (Meter-Bus)? With a Arduino or RPI? Maybe a M-Bus to serial is the way to go?
If you want to connect as a master: For a quick start: go with the RPI and have a look at the openmuc jMBUS lib: https://www.openmuc.org/index.php?id=48
I used it in combination with a ready to use (commercial) M-BUS-master-module offering a RS232 interface: http://www.solvimus.de/en/smart-metering/m-bus-oem-master/ pro: only needs one 24V DC supply, con: expensive (~30 €).
There is a simple MBUS-master circuit shown as part of rscadas libmbus: https://github.com/rscada/libmbus/blob/master/hardware/MBus_USB.pdf
In http://openenergymonitor.org/emon/node/1944 user Trystan Lea showed how they used the interface successfully. He also referenced a (required) step-up DC/DC converter (XL6009). Sorry - I was not able to get a direct link to the relevant post - look for '29/05/2015 - 15:40'.
To implement a slave: Use the TSS721A (TI - http://www.ti.com/lit/ds/symlink/tss721a.pdf) mentioned by @Rev1.0 or the NCN5150 (ON Semiconductor - http://www.onsemi.com/pub_link/Collateral/NCN5150-D.PDF).
You require some M-Bus transceiver IC like the TSS721A from TI. You can interface that transceiver directly with UART.
To be compatible with any common M-Bus master / M-Bus Software, you have to implement the protocol stack according to EN13757.
So yes, in general its totally possible to implement this on a Arduino or RPI. I designed a commercial M-Bus device based on an ATMega644p.