For OLC IMHO it's easiest to use Android device and XCSoar for
logging and then uploading to OLC. I suppose WinPilot running in
iPhone will be able to do the same, but I do not have experience on
that.

Logger with Bluetooth connection would be a nice feature. We have
IGC approved FLARMs with Soartronic BT modules, so we can
download IGC files using XCSoar. (XCSoar can also declare tasks
to FLARM logger, and show FLARM traffic on moving map during the
flight).