I purchased a SanDisk CF reader for the purpose of installing OpenBSD on Soekris Net4511 and accessing the pictures I take with my Canon PowerShot A100. (Note that the ImageMate and the SecureMate are not identical products. It appears SecureMate is not supported in OpenBSD).
Plug in the ImageMate, insert the media and boot your machine. At the time of writing, my machine cannot find sd0 unless it is in place at boot-up. I don't know if this can be fixed with a kernel tweak. If I unplug the SanDisk reader, X appears to crash, leaving a hard reboot as the only option.
priceless$ sudo mount /dev/sd0i /mnt priceless$ cd /mnt priceless$ ls -l total 34 drwxr-xr-x 1 root wheel 16384 Jan 1 1980 ./ drwxr-xr-x 15 root wheel 512 Nov 3 22:12 ../
umass0 at uhub0 port 1 configuration 1 interface 0 umass0: SanDisk ImageMate CF-MS, rev 1.10/0.12, addr 2 umass0: using SCSI over BBB-P scsibus0 at umass0: 2 targets sd0 at scsibus0 targ 1 lun 0: <SanDisk, Imagemate CF-MCF, 0101> SCSI0 0/direct removable sd0: 122MB, 399872 cyl, 4 head, 0 sec, 512 bytes/sec, 250368 sec total