In Germany I've been using the DB Navigator app and in Austria the OBB app for planning journeys and booking tickets. What is good about them is that they don't just deal with the train portions of a trip, but everything, if its necessary to take multiple trains and multiple busses it displays the information for all, and lets you purchase the ticket/s for everything. Making it very convenient.
Is there anything similar that can be used for traveling through Italy?
Good question, I’ll be following to see what others may be using. In the past I’ve consolidated all of my reservations using the tripit app but as far as I know this app doesn’t give the ability to make purchases within the app like you outlined.
The SBB app will work much the same for trips within Switzerland, and tickets will cover trains, buses, cable cars, or whatever is required.
For rail travel in Italy, the Trenitalia app will provide tickets for most of the country. Italo Treno provides a competing high speed rail network covering most of the larger cities, so you could also use their app.
For rail tickets in a much wider area of Europe (including the two main networks in Italy), have a look at the Trainline app - https://www.thetrainline.com/?gclid=EAIaIQobChMIkZDQwaa2-AIVcj6tBh1aPgPkEAAYASAAEgKe-PD_BwE&gclsrc=aw.ds . As I recall they may charge a small service fee but in the overall cost of a European holiday, I don't find that to be a problem.
