I've read in another forum that the live blessings over live shows are valid, but in that case the blessing was done by a Pope. They argued that the recordings are not valid, hence my question.
The apostolic blessing the Pope gives at the end of his
Urbi et Orbi address on Christmas day and Easter day, is the only blessing for which you can obtain an indulgence by receiving it over live television, radio or the internet.
I don't know for sure, but as making the sign of the Cross over the object is integral to the blessing of objects (and in some cases, the use of holy water), it would be reasonable to assume that the priest has to be physically present with the object.
However, the blessing of people is a little bit different, I think, as this blessing is effectively a prayer (e.g. the blessing at the end of Mass). What constitutes being blessed in these situations? Are the people in the cry room blessed at the end of Mass, even if there is a physical wall between them and the priest? That kind of blessing is a little different.
We distinguish between invocative blessings (prayer asking God for a blessing, e.g. grace before meals) and constitutive blessings (a prayer setting something aside for a sacred purpose and making it holy, e.g. blessing of liturgical equipment). But I don't think I'm the best one to explain this well