For "buddy SAR" some of the basics (whistles, signal mirrors) are going to work better than an avvy beacon. Of course whistles and mirrors require that you be conscious.

The one advantage of an avvy beacon is that you don't have to be conscious. Relatively few people have avvy beacons, but if you and a buddy already both have them, then there's no overriding reason not to carry them.

I just think the circumstances where they'd be useful in non-snow conditions would be so limited that it wouldn't be worth carrying them. You'd basically have to see your buddy fall but then not be able to see where he landed (dense brush or something). You basically have to have a pretty good idea where your buddy is but for some reason not be able to see him in order for an avvy beacon to be useful. Great in winter when you just saw him get buried in snow and saw about where he is, but I'm having a hard time imagining an equivalent scenario in the summer. Maybe a rockfall/landslide, but the chances of surviving such an event (if it's big enough to completely bury him) are slim, and, unlike snow, any sizeable rockfall is going to be hard to dig someone out from.

HJ