I did a Philmont trek this summer and the other adult carried his I-phone and a solar charger and - while I probably would not have if it were up tome - the gps data was helpful on a couple of occasions and fun to know elevation going up Baldy.  The panel just hung from his back pack and worked fine.  Would arrange to face sun while stopped for any significant length of time.  Used it to charge the Garmin "wrist gps" - which was quite fun if not essential.