I don't know how feasible this is, but a demo would be totally awesome. I am guilty of just having a demo video myself, and I think that it really cuts into my sales in a ton of cases.
Any game or app for that matter can benefit from a demo, trial or similar. Even though 5 euro is not a lot, it's still money. As there is so much low-quality stuff out there, customers are sceptical about buying something they haven't tried out to some degree.
