This is interesting. Similar services seem to be:
1. GumRoad (5% + 25cents)
2. InstaMojo (5% + 30cents)
3. e-junkie (it's complicated)
4. Pulley (per month starting from $6)
Pulley seems like the most promising to me (nice UI + appropriate pricing model).
But what I am really interested in is a store model, where there are categories, and ratings and users can discover more stuff and generic enough to host music, apps, etc. In short, an amazon for digital goods. And slim processing fees.
The tricky part is handling VAT for some geographies (such as Euro). What I would love is a service which either: a. Handles all VAT concerns b. allows me to limit sales for such countries. (to an Indie seller it can be a hassle).