I had a couple of apps and I have to say there were brilliant.
This one was my most favoutite
https://play.google.com/store/apps/details?id=com.independentrip.viadelaplata&hl=en
It's worth paying the 1.99 fee - there is a free version but I found the accommodation information useful. The app is in a few different languages, has text, elevation profiles and photos. There were a few occasions when the photos were very useful in keeping us on the trail. There is also information about towns, services and accommodation. Really a GREAT little app.
You will need to get the Silver route and the Sanebres... but worth the money
I also used a WISE PILGRIM app. I have this for the
Camino Frances too and I did find it a goo addition/tool
And the GRONZE website was also a tool I used a lot... there's no app but I just had a link to the site on my phone.
I found that these three worked very well together, coveed most bases and seemed to answer all my questions. I did also download the kindle version of Gerald Kelly's book... which was also good but the apps were my go-to point of reference.