creating mp3 device playing sound in specific time
Instead of using a VS1003 and a micrcontroller, you could do that with just a VS1005G using the internal flash. The VS1005G has internal real time clock, and the player software and the short MP3 file(s) could all fit in the internal 1 megabyte flash. You can also add SD card or external (nand) flash to play longer files. When you are waiting for the RTC alarm, the VS1005 chip just uses a few microamperes.