Hi Raphaël,
Indeed, live time stretch is not that simple.. but now looping hardware has a decent processor with the iphone/ipad, i think its possible. If you could do that, you would have the most wanted loop device/software on this planet

Its also the only way i think to see this wonderful software live in big gigs and bands.. very seducing!
Here they do some midi sync over wifi:
http://www.youtube.com/watch?v=FoVGvvMSCNMand electro harmonix figured out to slave midi on loop hardware
http://www.ehx.com/products/2880thanx for your quick reaction!
Rd