If you have a BlackBerry 10 smartphone, as the Z10 or the Q10, sometimes you will miss some app: the platform is very new, so, except for super popular apps like Twitter, Facebook, or similar, there is some deficiency.
In the long run the problem will be "fixed", since on BB10 apps can be programmed using almost any programming language, giving "easy life" to app developers, but in the short run we can feel something missing, what to do?
Luckily, inside the operating system there is an Android 2.3 simulator (it will be updated to "Jelly Bean" in a few months)
Can we install an app we like on it?
Of course!
There are some limitations, there are some kinds of apps that wont work, as for example:
- Apps that access to Google account without asking a password (e.g: Gmail, Google+, apps that check your Google Play account for anti-piracy purposes)
- Apps that manage phonebook and/or SMS
- Launchers (you can install them, but, if you do that, you will lose the wonderful BB10 multitasking on Android apps)
- Widget and live wallpapers (because without a launcher are useless)
- Apps that manage network and APNs
- Apps that contain more thans one app (for example the latest versions of Google Maps, contain 4 apps)
- Apps that embeds a Google Maps view (unless you install Google Maps)
- Apps that install or uninstall other apps
- Apps that use the direct audio access (Skype, Shazam, Videogames)
An average app will work, for games the compatibility is low, but you can try, it's free 
First: find the APK of the Android app
If you have a phone/tablet with Android you can use ES File Explorer to get it. Or you can use BlueStacks, there are dozens of ways, we can discuss them on the forum.
Second: convert the Android APK in a BlackBerry 10 BAR
For converting your app you can follow the long path, register as a developer, install a boatload of commandline programs and swear for a whole weekend, or you can just use the automatic service offered by apk2bar.unker.net.
Yes, just upload your APK on http://apk2bar.unker.net/ and in a few minutes you will have a BAR, ready to be installed 
Third: enable developing mode
Open settings and select "Security and privacy"
Now, select "Development Mode"
Enable "Use Developing Mode"
Now you will be forced to set a password for your deice: in fact, when the developing mode is enabled, you can add, launch, terminate, "spy" the app, the browser, and, in some cases, change their behaviour: if it would be possible to enable it without a password, it would be dangerous.
Fourth: install your BAR
Once you enabled the development mode, you can install all the apps you want.
Install this Chrome extension, write the IP address of your device in the options (if you don't know it, follow this guide) then access it by browsing to the address https://ip.address/ (remember to write the S after http)
Write your password, now you can install all the BARs you want! 
If I wasn't clear enough, let's discuss it on the forum.
