arduino - bluetooth - clarification.

hello
I need some clarification guys
I want to create a project with arduino and a bluetooth shield, here is the idea, I want to connect the arduino with another device then make the device send data to some website,
for now I only have a non complete idea, I am not sure if the arduino can control devices such as phones, laptops. i figured to come here and ask for guidance, I want to send data from arduino to a phone and make the phone print that data somewhere online. can it be done?
i found that some shields are pretty easy to connect with a phone or a laptop but I couldn't find how to control them from the arduino, I only foundthe opposite. Apps with a terminal where you type the commands that are already programmed in the arduino. can anyone point me in the right direction?
I may only need to send a trigger to the App and generate the data inside the app.
and if I try to code a customized app, would i be able to get the signal from arduino? and would it be hard to code? I mean would I need to analyze the signal?, etc etc
looking forward for your positive response.