The Wikipedia Android App description translation feature is pretty cool! I played with it a bit, and here's one piece of advice: allow showing source descriptions in more than one language. Currently you can select one source language and one target language. It can be useful to see more than one. For example, if I translate from French to Hebrew, it can be useful to see also the English description. It's not just a matter of which language do I know better; both the French and the English descriptions can give me good ideas for writing the translation.
Something similar is already done in the Translate extension, which allows the user to specify "assistant languages". The ultimate source language is always shown (on translatewiki and on Wikimedia sites this is always English), but other languages are shown in the sidebar if the user chose them and if the strings were translated into them.