[khedoros1]

You can still do that pretty easily, but most software doesn't release as separate apks outside of an app store (and particularly the Google store).

There are websites that provide apks, but I'm not sure of the legality there, and I'm not positive that they're unmodified versions of the software.

[toast0]

There's not any useful UI on android, but apks are signed (at least the jar is) by the developer, so you could check if it had been modified if you get the signing certificate from a Google Play install and see if that's the same certificate that signed the apk you download from who knows where.

You still have a potential issue if there's native code: Google Play makes it possible to build separate apks to support the different flavors of native code, so you need to grab the right apk for your phone, if the developers don't provide a web download with all the native code in one package.