To create a mobile language lesson with QR codes teachers can attach QR codes to objects in their classrooms or schools. Then have students try to identify those objects in the language that they're trying to learn. To check their answers students can scan the QR code and hear the correct answer on their phones or tablets. There are two tools that make it easy to create QR codes that will launch audio files on students' smartphones and or tablets.
Vocaroo is a tool that I've written about many times in the past. On Vocaroo you can quickly create a short audio recording. When you save the recording you can opt to have a QR code generated. When it is scanned that QR code will launch your audio file on your students' smartphones.
QR Voice is a free tool that allows you to create QR codes that when scanned will play a short audio message. To create your message and QR code you can record a voice message by clicking the microphone icon on QR Voice or you can type in your message. Either way you're limited to 100 characters. QR Voice is offered in 38 languages.