This is what we use at work:

http://www.brother-usa.com/PTouch/modeldetail.aspx?PRODUCTID=PT2700

I do all the autopilot installs and application control installs.  What I usually do is put what I want printed on the label then put in spaces that make it twice as long, then wrap it over the harness or cord and stick it to its self.

It accepts all sorts of size tape and the tape is indoor/outdoor.  The tape holds up very well on implements out in the weather.