Many gases and polluting elements exhibit absorption lines in the mid-wave infrared, thus light sources emitting in this range are sought after for sensing applications. Although it is possible to reach such long wavelengths with edge emitters, their large power consumption is not compatible with the realization of portable devices. On the other hand VCSELs, already consolidated in smartphones for near-IR sensing, would be an excellent fit. Increasing the wavelength requires designing new VCSELs, based on low-gap materials such as InAs/GaSb alloys, although introducing a number of problems concerning current injection/confinement and electro-opto conversion. For the transverse confinement, a viable replacement of the oxide apertures of AlGaAs VCSELs is given by buried tunnel junctions (BTJs).