I am trying to combine information from one exchange with information and actions I'd like to take in another. Is it possible to use Qt Bitcoin Trader to share information between exchanges?
To illustrate a simple example: Let's say I am looking at the price development of ETH/USD on bitstamp and would like to trigger a buy on btc-e when the price on bitstamp increases. Can that be done? How?
As far as I know, no, it only connects to one API at a time. You might be able to open more than one instance of it, but I don't see any way for the two to connect. You'd need a different program or to create something yourself since it sounds like you want trigger rules that utilize both exchanges, like "if price on Bitfinex goes below 95% of BTC-e price, sell x btc on BTC-e" etc.
I actually hadn't thought of opening more than one instance of qt at a time. If it works I might have to try arb trading with a setup like that

. I could see something like that being a useful feature someday... with more than one api logged in at a time.