It's a simple & straight questions. Just think about an app that when you found it, you first thought would be - "OMG!!! That's it" - or smth like - "I wish I could have found/written/idealized it before". Don't need to be a bioinformatical swiss knife or a McGuyver paper clip. Just smth that would make your life much happier/easier.
My example is quite simple. I really wish that some sort of Monte Carlo Simulator of Generic Urn Models (population genetics rlz!) just appear in the net, with a nice, clean and well documented API (written in C) and bindings for my favorite scripting languages. That's what I really miss, right now. What's your story?
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I'm considering to start a bounty for this question. Maybe the first answer to get 10 up votes. Where are people's whishes? Don't be afraid, bionformaticians like me are lousy critics.