The geometrical properties of sigma models with target space a Jacobi manifold will be here investigated. In their basic formulation, these are topological field theories -recently introduced by the authors -which share and generalise relevant features of Poisson sigma models, such as gauge invariance under diffeomorphisms and finite dimension of the reduced phase space. Analogously to Poisson sigma models a generalisation is possible, which is fully dynamical and yields a Polyakov string action with target space a Jacobi manifold. After reviewing the main novelties and peculiarities of these models, we further analyse the target phase space and in particular the dimension of the latter, which results to be finite, as well as the integration of the auxiliary fields for contact and locally conformal symplectic manifolds, resulting in a Polyakov string action with background metric and B-field related to the defining structures of the Jacobi manifolds. .