  With the advent of the nanosat/cubesat revolution, new opportunities have
appeared to develop and launch small ($\sim$\ts 1000 cm$^3$), low-cost
($\sim$\ts US\$ 1M) experiments in space in very short timeframes ($\sim$ 2\ts
years). In the field of high-energy astrophysics, in particular, it is a
considerable challenge to design instruments with compelling science and
competitive capabilities that can fit in very small satellite buses such as a
cubesat platform, and operate them with very limited resources. Here we
describe a hard X-ray (30--200\ts keV) experiment, LECX ("Localizador de
Explos\~oes C\'osmicas de Raios X" -- Locator of X-Ray Cosmic Explosions), that
is capable of detecting and localizing within a few degrees events like
Gamma-Ray Bursts and other explosive phenomena in a 2U-cubesat platform, at a
rate of $\sim${\bf 5 events year$^{-1}$.} In the current gravitational wave era
of astronomy, a constellation or swarm of small spacecraft carrying instruments
such as LECX can be a very cost-effective way to search for electromagnetic
counterparts of gravitational wave events produced by the coalescence of
compact objects.
