This is the (scientific) translation for 'Lebenszeichen'.

When incubated over long periods, he said, Antarctic samples show signs of life because dormant microbes have become activated. -N.Y. Times

An expression such as "signs of life" might conceivably be used in English in the sense you used it by bilingual Fr-En speakers familiar with "Je n'ai pas eu de signes de vie de lui depuis quelques temps" ("Haven't heard a peep out of him in quite some time"; lit: 'I haven't had signs of life from him for some time') but I would find this very unusual from the mouth of a monolingual.

Otherwise this phrase would be limited to the literal context "alive or dead".

It is 9.00 on Saturday morning. I desperately need to borrow my neighbour's lawnmower. But his curtains are drawn, the cat is waiting impatiently next to the milk bottles and the newspaper on the doorstep. I could say: I see no sign(s) of life from next door.
And even if I ring, he'll probably not hear me: judging by the party there last night, he will be "dead to the world" for another hour or two.

This kind of idiomatic use of the phrase came to my mind straightaway.