Wifi-remote operated explosives - Boston question

It's still unclear if the bombs were remote detonated but i'll go ahead and ask anyway.

Rather then a cellphone triggering the detonation from a call like i've heard,
would it be possible to detonate from anywhere on the planet using the internet?

My grandpa was discussing this with me, the person could have been in another country and had an American group assemble it and place it or even a tourist, then they could be watching it live to know when to detonate.

Sounds kind of implausible if you ask me though, since Echelon would likely pick up that signal and trace it unless you can mask something like that?

Considering the bomb casings were 6 liter pressure cookers (as was reported in the FBI news conference earlier). I would think that no trigger device was necessary. This would allow for the bomb planter(s) to be no where near the area once the bombs detonated.

With that casing, it leads me to believe that a chemical concoction was used that built pressure over time. However, it is my gut feeling that they were supposed to go off 2 hours before they did. I am thinking the concoction took longer to build the adequate pressure to go off than when it was intended to, albeit they were pretty close together. Which would seemingly require more than one person to pull off.

This would also give credence to why they went off after the race had been going for over 4 hours and not the more opportune time (as has been mentioned in the media) at the two hour mark when there would have been more of a presence of people.