  We investigate how emergent nematic order and nematic fluctuations affect
several macroscopic properties of both the normal and superconducting states of
the iron pnictides. Due to its magnetic origin, long-range nematic order
enhances magnetic fluctuations, leaving distinctive signatures in the
spin-lattice relaxation rate, the spin-spin correlation function, and the
uniform magnetic susceptibility. This enhancement of magnetic excitations is
also manifested in the electronic spectral function, where a pseudogap can open
at the hot spots of the Fermi surface. In the nematic phase, electrons are
scattered by magnetic fluctuations that are anisotropic in momentum space,
giving rise to a non-zero resistivity anisotropy whose sign changes between
electron-doped and hole-doped compounds. We also show that due to the
magneto-elastic coupling, nematic fluctuations soften the shear modulus in the
normal state, but harden it in the superconducting state. The latter effect is
an indirect consequence of the competition between magnetism and
superconductivity, and also causes a suppression of the orthorhombic distortion
below T_{c}. We also demonstrate that ferro-orbital fluctuations enhance the
nematic susceptibility, cooperatively promoting an electronic tetragonal
symmetry-breaking. Finally, we argue that T_{c} in the iron pnictides might be
enhanced due to nematic fluctuations of magnetic origin.
