I will be on RS tour. I was thinking of using the WienMobil app for payment and use of transportation. I can't seem to save anything on the app so I guess I will use Google maps for navigation.
I would most likely purchase a Vienna City Card for 48 hours and a single ride. Once I purchase how do I validate with my phone before I get on the trams or busses and do I need to "check out" before I leave the bus/tram?
Any tips with the app?
It's been awhile since I was there but basically once you activate the card, it's good for the relevant time period and then it expires. So you do not need to check out when you leave the bus or tram. Just present it when entering and you are good to go.
This will also give you some information. https://www.viennacitycard.at/view/FAQs
Don't confuse the 48-hours Vienna City Card with the 48-hours Vienna Transit Pass. You should buy the latter; IMHO the City Card does not pay off, giving you reduced entry fees at certain sights.
Having your public transport ticket stored on your phone is enough. You can enter and leave any means of public transportation at any time without having to show it. If there is a random check of tickets, which is rather unlikely, you must prsent it to the inspector. So make sure that your phone battery is charged. (Therefore I preferred the printed version, just to be sure.)
Google maps is not very reliable regarding public transport. The best app for getting from A to B by public transport in Vienna is this one: https://www.vor.at/en/timetables-mobility/vor-apps/vor-anachb-app
I use Google Maps in Vienna many times each day - never lets me down.
I also think that you are making this too complicated. Just buy a 48 hour transportation pass from one of the many, many ticket machines at stations all over Vienna. The machine allows you to determine the validity period, in English. No need to actually validate in a machine - the dates are already printed on the ticket. The transportation pass is valid on all forms of transportation including buses, trams, subways and s-bahn trains within the city limits of Vienna. The public transportation system in Vienna is based on the honor system. There is no check-in/check-out on any form of public transportation. If you do end up needing to validate a ticket, then you do that using the blue boxes at every station, on buses and on trams.
The Vienna City Card is unnecessary.
