raindrops on the car's windshield with wipers(easier system)

Hello everyone!

I'm having a trouble here,I want to make raindrops effect on the windshield of my car,but not like in driveclub with their complex system,I want something easy that a smartphone can handle.

I did a small research and found a perfect example - Colin McRae Rally 2004. It has amazing rain effect,and it was made to work properly in 2004,so this should be asy to d with a smartphone,right?

I don't know how exactly the system works,is it shader or particle system,but I recorded an interesting video - by replacing the textures I was able to see that raindrops are made of...particles or some sort... Just take a look at this http://www.youtube.com/watch?v=dhQBKNTNwPE

And here are some of the textures for testing purposes http://www.mediafire.com/download/rly2teli3sdxbff/Rain_windshield_textures.rar

I'm sure that this is shouldn't be a complex system,since it's that old... I hope someone can help me out,guys!