fc-simtool can operate on SIM cards that sit inside a Calypso phone or FC
development board, as opposed to the more classic case of operating on a SIM
inserted into a dedicated card reading/programming station.  However, this
special Calypso mode of operation works in an unusual way: instead of invoking
fc-simtool (or fc-uicc-tool) directly, you have to run a front end program
called fc-simint.  fc-simint loads and runs simagent on the Calypso device the
same way how fc-loadtool loads and runs loadagent, then it passes the open file
descriptor to fc-simtool via the special internal-use-only -C option.

fc-simint and its simagent back end reside in the FreeCalypso host tools
package, not in FC SIM tools.  As of this writing, a packaged release of FC
host tools with fc-simint and simagent.srec included has not been produced yet.
A new fc-host-tools-r15 release is planned for the near future; if you need to
use the new feature right now and can't wait for the upcoming release, you will
need to get the current code from the Hg repository:

https://www.freecalypso.org/hg/freecalypso-tools/

Please beware that if you are not able to wait for the upcoming release, you
will have to install the special ARM7 gcc toolchain and compile simagent
(Calypso target code piece) from source.