Programmer Skyfloogle, has released Red Viper, an updated virtual-boy emulator for the 3DS.

From the github description: "A Virtual Boy emulator for the Nintendo 3DS continuing mrdanielps's work on r3Ddragon, which is itself based on Reality Boy / Red Dragon. It uses a dynamic recompiler with busywait detection and a hardware-accelerated renderer to achieve high performance on the 3DS's limited hardware."