The SIMtrace project has from beginning on been designed to not only monitor the communication between a card and the reader (e.g. a SIM and a phone), but also to emulate cards. This card emulation functionality has never been implemented, at least not by the osmocom community, and the project has been hibernating for quite some time. A year ago, the SIMtrace project has been revived. The now old and deprecated micro-controller has been replaced with ARM Cortex-M, but the initial design remains. This change forced us to rewrite the code from scratch, and this is now the SIMtrace 2 project. Monitoring the communication is still available, even with increased stability, but this fresh start was to opportunity the also implement the other long awaited features.
Card emulation is finally there. Is it currently in it's beta phase, but has already been successfully tested. It can even be used in combination with the recent osmo-remsim project, allowing to use multiple cards at remote locations. While it is not completely emulating a card since it only forwards the traffic to a card present in another reader, we are currently working on also providing this functionality. So, feel free to try it out yourself, and let us know using the SIMtrace mailing list if you find any issues. The card emulation wiki article will be updated as we continue on our journey to make SIMtrace the tool it was intended for from beginning on.