Assuming these neigh-invulnerable wonders can survive the g-forces, we could mass-manufacture containers to store tardigrades and launch them blindly into space with railguns. The containers would be designed so the g-forces of impact would crack them open.

When the very rare occasion happens where a container impacts a planet or moon, the tardigrades would be exposed to the environment. If it could support the basics of life, after a few thousand years, they would be present enough in the environment that any alien life that exists there or might develop there will eventually notice them.

If the tardigrade DNA contains a message from Earth, it might be discovered and decoded.

It could be the best way to ensure that our existence won't be forgotten in the scale of billions of years.