In the spirit of sharing, I'll share a few useful apps I've added to my arsenal of tools.
1. For my iPad - Draw Maps: Map Notes by Bluefield GIS, Inc. for iPad
This is a map app that allows me to scribble notes (it really helps if you have an apple pencil) on the map. I use it on the field to draw sketches and make notes of locations of split points, turnarounds, etc.
2. For my iPhone - Solocator for iPhone.
I just discovered this app and not yet used it on the field, but it looks very promising. The app itself is $.99 with the option of purchasing additional tools for another couple of bucks. This app stamps your course photos with the nearest address, GPS coordinates, altitude, and other data along with any notes you make. You can even edit the descriptions after you've left the field. I like to give any course photos I take to my clients. I'm looking forward to using this on my next measurement job.
3. Google Sheets
I'm sure I'm not the only one using these, but I do all my course calculations on a google spreadsheet and use the Google Sheets app for iPhone and iPad to make entries while measuring. The spreadsheet I use was originally built by Duane, which he generously shared on http://racemeasure.com. I've taken his sheets and tweaked them for my own purposes and for optimal viewing via a mobile device. You can view my spreadsheet here - Shared Mobile CertSheet