Addons is too broad for the forum, you'll have to contact the manufacurers however I've never seen a 3rd party phone home from the popular developers (SolSPace, P&T, GotoLow, Expresso, PutYourLightsOn)...
The Licence check came in on version 2.9 (July 15, 2014), all it does is send some server details back to EllisLabs, heres the actual payload code for you to see :
$payload = array(
'contact' => ee()->config->item('license_contact'),
'license_number' => (IS_CORE) ? 'CORE LICENSE' : ee()->config->item('license_number'),
'domain' => ee()->config->item('site_url'),
'server_name' => (isset($_SERVER['SERVER_NAME'])) ? $_SERVER['SERVER_NAME'] : '',
'ee_version' => ee()->config->item('app_version'),
'php_version' => PHP_VERSION
Fairly safe. also I recall when they brought this out that the licence check is non destructive, it is for infomation purposes so you can manage your licenses better,
but I can't find it anywhere(found it). The code doesn't show anything other than the payload-ping though...
EllisLab has always taken a soft approach to license registration so we treaded very lightly here. You will never be locked out of your software nor will the behavior and output of your site be impacted by this in any way.