The Nordic Glide Wax utility for iPhone and iPod Touch, provides glide wax recommendations (Swix, Toko, and Solda) based on temperature, snow type, and humidity.
It's similar to on-line wax advice utilities, but this tool resides on your iPhone and can be used anywhere. Plus, it handles recommendations for all three brands at the same time, so you can mix and match based on your preference or based on what you've got in your wax box.
The Nordic Glide Wax utility (this goes to iTunes site) was created by Brian Drye. It's only 99 cents! If you've got an iPhone or an iPod Touch, then you ought to give it a try.