You can already do all of that with sierra charts. They have an API which you can tweak your own buy sell algorithms. The trick for me was to create a rely (i wrote mine in java) between mtgox and the trade feed in sierra charts.
as for the Trading API, all requests must be POST. You also do no specify the parameters in the query string. This is a low level secuirtyu mechanism for people sniffing urls, like your job, isp, router, etc...
Another great tool and easy to setup is to download and install the firefox plugin call Poster. This plugin lets you perform any type of HTTP request. I have multiple poster dialogs opened up for each of the actuions i commonly do. And tweak the parameters as needed. I trust this a little more (dont know why) then manually typing these at the command line.
Ive found this is a little faster then the website,since you are skipping the entire gui part.
If someone has some good ideas for a bot, maybe we can collab, right now i have to many other bitcoin projects im in the middle of working on, but i do have a little time to dedicate to a team working on a bot.
lastly if anyone has any concepts for a trading desktop app, thats another project i would like to use, cuz well, i dont really like sierra charts to much, between its lack of asthetics, and many quirks
happy trading =)