What you need on your PC:
1. POILoader v2.5.3 (or later)
2. sox.exe v14.0.1 (in the same folder as your POILoader.exe)
Step 1: Create your POIs
a. Open Mapsource and edit your POIs.
b. Save as AnyName.gpx
Step 2: Create your POI Icon (Optional, otherwise your POI will just be a small grey circle)
a. Create a BMP file no larger than 24 x 24 pixels
b. Save it as AnyName.bmp
Step 3: Create your Voice Message
a. Create a WAV file in PCM 44.100kHz 16 Bit, Mono format
b. Save as AnyName.wav
Step 4:
a. Copy those 3 files (from Steps 1, 2 and 3) into the same folder
Step 5:
Run PoiLoader, and follow the instructions.
[Screen 1] Welcome [Next]
[Screen 2] Save Options : Garmin Device [Next]
[Screen 3] Device Settings : 'your SD card' [Next]
[Screen 4] Install new custom POI's... [Next]
[Screen 5] Select 1. datafile directory (where AnyName.*** was saved), 2. units and 3 'Express' Mode
[Screen 6] Congratulations!

Notes:
1. Step 1: These are location(s) where you want the nuvi to remind you of the doa, in this case, just near your home, office, etc.
2. I skipped Step 2, as I like the small grey dot

3. The wav file is attached, compressed.
4. For nuvi's capable of MP3's, you do not need to use sox.exe, but follow Step 3.