Interesting query glekichi, I've been giving this a little thought...
First, it's a can of worms. I don't think there is going to be an easy answer. The GPS would be useful only in certain types of search patterns (i.e: creeping line, expanding square -there may be others, I'm not totally familiar with the processes) but of little if any real guidance benefit in a contour search where the pattern location is defined by a geographical feature (mountain top) and subsequent passes dictated by the surrounding terrain. Definitely worth more thought and investigation though.
With a pattern like a creeping line or expanding square, the GPS may be able to provide significant benefit though -although again probably constrained by terrain considerations unless over a featureless area or significant body of water.
There are some GPS units that can define turning points as a distance and bearing from a given geographical coordinate -I am pretty sure that my GPSMAP296 can do this- so if you can programme 1 point in this manner, I can see no reason that you couldn't programme as many as may be necessary to define these types of search patterns. Again I'm pretty sure that if you can define it, you could save it (as a route perhaps?) making it reusable and relocatable presumably by changing the coordinates of the defining 'start' point.
One thing that you would need to be very careful of is, as alluded to earlier, be careful that your search-pattern does not raise the possibility of CFIT as a consequence of slavishly following the GPS guidance without consideration of terrain or in circumstances of reduced visibility.
I've had a look at the results of a search as suggested planit, but have not seen anything in the 1st few pages beyond requests for developmental funding for commercial applications (probably very expensive!!!) and no sign of any software available to assist in planning/uploading a search pattern to a GPS. Would be very interested in any links you may have found!
Hopefully others will add their thoughts/knowledge to this thread... interesting stuff, keen to see where it goes!