Obviously it would need to offer a CRUD interface to some form of persistent storage, namely one that I can easily access anywhere; that makes the most idea solution a file in my home directory, or something accessible over the network.
It would have to support some notion of "Tagging", every entry should be able to be tagged under multiple names and queried accordingly.
A list view comparable to the collapsible "Groups" in most instant messengering softwares buddy list, would be a perfect way to view tags, particular when combined with the ability to search todo's by tag and other criteria: like date, title, and all other data.
While software oriented towards managing the software life cycle might be useful, I need something of a more general nature. The only real short coming of Google Tasks is that while it integrates into Mail and Calendar quite nicely, it unfortunately has no real concept of tagging. It's more of a gimmick then a useful feature.
In all probability I could munge together some AWK scripts and an SQLite database to get exactly what I want, hahahahahahah! And maybe someday write a graphical front end. Hmm...