BASEL, Switzerland — No one knows what it will look like. No one knows what it will cost. But the forthcoming — and thus far nameless — smartwatch announced by TAG Heuer, Google and Intel on Thursday became the watch to watch at the giant Baselworld watch fair.

The smartwatch is the most dramatic counterstrike yet by Swiss watchmakers against the potentially seismic entry into the field by the Apple Watch, which goes on sale next month.

The timing was also dramatic: on the second day of Baselworld, a convention where centuries-old Swiss houses still unveil limited-edition artworks for the wrist that can cost more than $200,000.

After the announcement, however, Jean-Claude Biver, chief executive of TAG Heuer, said that the smartwatch is in keeping with an industry built on intricate mechanical timepieces. (After all, the pedigreed Swiss watchmaker has always positioned itself as forward-thinking; TAG stands for “Techniques d’Avant Garde.”)