To elaborate a little bit more. I have a Zumo 595 and 665 that I am running in conjunction with my ipad mini 3. My 665 is the primary voice/direction GPS that is sync'd to my Sena 20S. I then sync my iphone to the 595 so i can see the caller id info on my GPS screen and make and receive calls through the 595. This allows me to keep my phone in my tank bag. I also listen to XM radio on the 595. That't how I fill most of the time in Rally's. If you are using the ipad or other device as the main routing GPS you could use it for your music streaming service of choice or audio book streaming as well.
On my ipad it has cellular service buy I only buy the prepaid air time for when I know I'm going to be needing it. I have always had enough doing it this way. And in a pinch I could hot spot off my phone.
As for other apps or gadgets. I will have the SpotWalla site up in the browser. I like to keep track of the other participants during Rallys where there is a public page to follow. It lets me know where the pack is and where I am in relation to others. I use a Spot 2 device with the spotwalla service. I have used Rever for tracking my shorter rides around home. I use it stand alone when I don't have the Spot with me or a spotwalla trip set up to keep track of my travels.
I have a stylus on a short retractable cord (to keep from losing it) to allow simple functions on the ipad if I have gloves on that do not work with the touch screen. Although most apps require 2 fingers to pinch and zoom around in them. Other apps for weather such as AccuWeather or Weather are useful. Google Earth can provide some cool features as well that are different than just google maps. Although I do not route using this.
One App I use a lot is the simple Notes app. When I'm riding for a long time, things will pop into my head that I want to remember later or to start a list of things I need to do, check, buy, etc.... I just make a quick note to remind myself later.
Brian