How would I go about detecting magnetic monopoles? A question needed for a "solid" sci-fi author: How to detect a strong magnetic monopole? (yes, I know no such thing is to be found on Earth).
Think of basic construction details, principles of operation and necessary components of a device capable of detecting/recognizing a macroscopic object emitting magnetic field of equivalent of order ~0.1-10 Tesla near its surface, but with only one pole, reliably distinguishing it from normal (2-pole) magnets, preferably at a distance.
Preferably a robust method, not involving extremely advanced technology. Detect the presence, possibly distance (or field strength) and direction.
I know of SQUIDs, but these concentrate on extreme sensitivity. I'm thinking of something less sensitive but more robust (like, no need for the monopole to fall through the loop) and still able to recognize a monopole against a magnet.
Also, how would such a macroscopic object behave practically? Such a "one-pole magnet" about the size and strength of a refrigerator magnets - how would it behave around ferromagnetics, normal magnets and so on?
 A: Blas Cabrera designed and built a magnetic monopole detector.  Here's one report on it:

First Results from a Superconductive Detector for Moving Magnetic Monopoles. B. Cabrera. Phys. Rev. Lett. 48 no. 20, 1378–1381 (1982). Princeton eprint.

(Old link at http://www.slac.stanford.edu/cgi-wrap/getdoc/ssi82-025.pdf now dead and not archived by the Wayback Machine.)
A: In this I am replying to the question stated about macroscopic monopoles, as you describe them. 
A magnetic monopole would attract magnetized matter,  falling in strength over distance by 1/r^2.
You would know it is a monopole if you go with your normal everyday compass and your spaceship all around it and see that the compass is pointing always north, or always south, all around. This could be done quite a distance away if it is a monopole in the range of Tesla, as you seem to ask.
As long as the dimensions are macroscopic, as simple compass will tell you if is a monopole using it to map it all around. A macroscopic monopole would be attracted to the opposite side pole of a dipole magnet  and to ferromagnetic materials just as the dipole magnets attract them. There are commercial instruments for measuring magnetic fields.
You can see I am a science fiction fan. My favorite is Terry Pratchett, where he talks of magnetism as "the love of iron" :).
A: Consider the motion of a magnetic monopole in a completely symmetric Maxwell system, where 
$$
\nabla\cdot {\vec B}~=~4\pi\rho_{mag},
$$
and 
$$
\nabla\times{\vec E}~=~4\pi{\vec J}_{mag}~-~\frac{\partial{\vec B}}{\partial t}
$$
The first equation is then a Gauss’ law for magnetic monopole charge, and the second is a magnetic current form of the Maxwell-Faraday equation.  For the occurrence of a magnetic monopole flying through space this will act as a transient current.  The last term on the right hand side is a displacement monopole current in this case.  The left hand side will by Stokes’ law $\int\nabla\times{\vec E}\cdot da~=$ $\int{\vec E}\times d{\vec l}$, produce an electric current in a loop.  So the right hand side could be measured by the torque this magnetic field induces on an ordinary magnetic dipole.  The right hand side measured in a solenoid.  If the left hand side and the last right hand side term do not equal each other in the standard form of the Maxwell equation with ${\vec J}_{mag}~=~0$, this would be a signal for the detection of a magnetic monopole.
A: Chapter 6.11 of Jackson's Electrodynamics mentions that Dirac's quantization argument fixes the strength of a magnetic monopole, were one to exist. Jackson goes on to say:

...Their coupling strength is enormous,
  making their extraction from matter
  with dc magnetic fields and their
  subsequent detection very simple in
  principle. For instance, the energy
  loss in matter by a relativistic Dirac
  monopole is approximately the same as
  that of a relativistic heavy nucleus
  with Z=137n/2. It can presumably be
  distinguished from such a nucleus if
  it is brought to rest because it will
  not show an increase in ionization at
  the end of its range...

The method suggested wouldn't work at a distance, but it seems to cover the heart of your question.
A: Of course one could go about trying to search for monopoles with sophisticated apparatus in a similar vein as searches for dark matter and supersymmetry.
Or, one could follow the path taken by Castelnovo, Moesnner and Sondhi who demonstrated the existence of monopoles as emergent excitations in spin-ice: Magnetic Monopoles in Spin Ice (Nature, 2007). This answers quite definitely the question of do magnetic monopoles exist in Nature ?.
