It's a shame that any significant contact would wipe the Sentinelese out. Even a common cold infection would be the end of them.

If we wanted to learn anything about the Sentinelese, then perhaps we could use well-camouflaged camera traps, and other electronic eavesdropping devices. The moral considerations are difficult - it's a privacy breach, but the information would also be valuable not only to their descendants (should contact be made), but also to science generally. I think I would be happy if my Viking ancestors had been filmed 1000 years ago.