Let's stay in Switzerland to start with. Spending the night in a bus outside a campsite is not prohibited everywhere. But almost. If we also assume that nobody wants to spend the night at a rest stop (which is permitted in certain cantons), then the following cantons remain:

• BL: in certain municipalities,
• BE: in certain parking lots,
• FR: on official parking spaces,
• NW: with the consent of the public or private landowner,
• OW: for one night, "if no public or private interests are affected",
• SZ: partly permitted, ask the municipality
• TI: only on official pitches,
• UR: not prohibited in all parking lots - ask the municipality
• ZH: exceptionally for short periods with the owner's consent,
• ZG: with the consent of the owner
.

Source: tcs.ch

It should be noted that it is permitted to spend the night on private land anywhere in Switzerland with the consent of the owner.

The website Campofant divides Europe into countries where free camping is prohibited everywhere (even on private land with the owner's consent): Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Greece, Hungary, Macedonia, Montenegro, Netherlands, Portugal, Serbia, Slovakia, Slovenia; in countries where it is allowed on private land (with the owners' consent): Denmark, Finland, Great Britain, Luxembourg, France, Ireland; in countries where free standing is permitted for one night in one place (unless otherwise signaled): Belgium, Germany, Spain, Italy; and finally, the countries where wild camping is generally permitted (or not prohibited) remain: Estonia, Latvia, Lithuania (only outside built-up areas, observe prohibition signs), Norway, Sweden (observe prohibition signs), Austria (special regulations in individual regions, prohibition in Tyrol and Vienna and in nature reserves, prohibition signs) and Switzerland (see above).

And now to the mobile apps. If you ask around among van people, the apps listed below come up most frequently. What they have in common: users enter places and rate them.

• iOverlander - Good for North and South America
.
• REI MTB Project App - an app from the US outdoor store chain REI, contains mainly trails, but also camper sites.
• Trailforks - the trail app also shows camper sites.
• park4night - Europe, especially France
.
• Stayfree - Google Play App Store.

For wild bus vacations, it is also worth joining Vanlife Facebook groups, where there is a lively exchange about good and less good places, e.g. on the page of Vanlife Switzerland.
Finally, many full- and part-time vanlifers share their places to stay on Instagram. Which makes one thing clear: If you are looking for great independence with a camper van but don't want to spend too much time looking for a place to sleep, you need one thing above all: internet access.