Thanks.

FWIW, I just hacked together a really simple test case that seems to work.  I will post here for the benefit of anyone who may be interested in the future.

The serialization library is *really* nice!

Three files:
  - Test.h
  - Test_mex.cpp - creates a function that can be called from Matlab that un-serializes the object
  - Test.cpp - creates the archive.


================= <Test.h> ==================
#ifndef Test_h
#define Test_h

#include <ostream>

#ifdef BINARY_IO
# include <boost/archive/text_oarchive.hpp>
# include <boost/archive/text_iarchive.hpp>
  typedef boost::archive::text_oarchive OutputArchive;
  typedef boost::archive::text_iarchive InputArchive;
#else
# include <boost/archive/binary_oarchive.hpp>
# include <boost/archive/binary_iarchive.hpp>
  typedef boost::archive::binary_oarchive OutputArchive;
  typedef boost::archive::binary_iarchive InputArchive;
#endif

struct Test
{
private:
  friend std::ostream& operator<<(std::ostream& os, const Test& t );
  friend class boost::serialization::access;

  template<typename Archive>
  void serialize( Archive& ar, const unsigned int version )
  {
    ar & i;
    ar & d;
    ar & *p;
  }

public:
  int i;
  double d;
  double* p;

  Test()
  {
    p=new double;
  }

  Test( int _i, double _d )
  {
    i=_i;
    d=_d;
    p = new double;
    *p=d*2;
  }
  ~Test(){ delete p; }
};

std::ostream& operator<<( std::ostream& os, const Test& t )
{
  os << t.i << ", " << t.d << ",  " << *(t.p) << std::endl;
}

#endif Test_h
======================== </Test.h> ====================

 ======================= <Test_mex.cpp> ===============
#include "mex.h"
#include "Test.h"

#include <iostream>
#include <fstream>

using namespace std;

void mexFunction( int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[] )
{
  mexPrintf("Hello.\n");

  Test t;
  ifstream in( "serialize.out",ios_base::in );
  InputArchive ia(in);
  ia >> t;
  mexPrintf("%i\n",t.i);
  mexPrintf("%f\n",t.d);
  mexPrintf("%f\n",*(t.p));
}
================= </Test_mex.cpp> ================

=============== <Test.cpp> ==================
#include <iostream>
#include <fstream>

#include "Test.h"

using namespace std;

int main()
{
  Test t(1,0.1);
  {
    std::ofstream ofs("serialize.out");
    OutputArchive oa(ofs);
    oa << t;
  }
  cout << "original : " << t;

  {
    ifstream ifs("serialize.out",ios_base::in);
    InputArchive ia(ifs);
    Test t2;
    cout << "ready to import..." << flush;
    ia >> t2;
    cout << "done" << endl;
    cout << "restored : " << t2;
  }

}
================== </Test.cpp> ===================