Hi Matt,
The papery bark is reminiscent of Mel. Ericifolia but the spherical seed pod doesn't ring true to me so I lean towards it being something else ... what though - dunno!
Plantnet is a great ID source for NSW. You can search based on species or location. Local area of Penrith yields 5 Mel species. a quick check of these gives M. nodosa as a very likely match http://plantnet.rbgsyd.nsw.gov.au/cgi-b ... uca~nodosa