If you call the same number 10 times in a row, or let it ring for minutes, you can be reasonably sure nobody is home. Most people would at least get pissed and pick the phone up, if only to slam it back down.

Well now your phone is linked to the robbery. One call might be explainable but 10 is pretty suspicious, especially if you do it at multiple crimes.

I'm sure it's not too hard to anonymously get a phone number. Google voice perhaps?

That would only be anonymous to the recipient. Google still has a map from your actual account and phone number to your Google voice number.

Payphones.

Far too low-tech for HN.

It's easy. Tor + anonymous BTC purchase of VoIP. Getting BTC is the harder problem.

> If you call the same number 10 times in a row, or let it ring for minutes, you can be reasonably sure nobody is home.

If it has an automatic answering system, you can't "let it ring for minutes", and if it has the ringer turned off (and there are lots of people who, with an answering, do this by default) then it won't even ring at all (though you'll think it is ringing.)

Too late, the telemarketers already (effectively) doing this.

VoIP# -> unpublished home line (+ Mobile)

Home line 'protected' from autodialers by old fax machine, 4 rings then silence. Only political calls seem undeterred.

You'd let it ring for an hour?