Linux kernel module (tun) compilation for ARM device

We are currently working on a low-power Linux device which records sensor data in the field.

In order to run OpenVPN on the device, I need to compile the tun.ko module and/or recompile the kernel. I have the kernel source, but not the time or experience to get the job done.

I can provide direct access to the device, and can provide kernel source and hardware information.

Additionally, I would also like to reduce the filesize used by the Debian installation (it's currently about 750MB) so that I can fit it onto the 512MB Flash included on the board, as I believe booting from the SD card may not particularly reliable. In this scenario I would then use the SD card simply as a storage medium. This is optional, however.

If we can do this, there are some other upgrades we may wish to do in addition, for example writing a small terminal based curses program that launches when a user connects to the RS232 port and logs into the device, to make administration easier for field engineers, and some help on reducing the power consumption of the device.