We use the Bad Elf GPS Pro with our Ipad collector App. It is very easy and accurate to ~9' in most cases. All our work is done offline in remote Alaskan field locations. When we return to WiFi connection the sync process to ArcGIS online takes no time at all. I love my Bad Elf. Apparently they are working out a glitch in the display. Our team has 6 elfs and 1 display stopped working. Their customer service was some of the best I've ever experienced. We had a new one within days.