  The observation of Very High Energy gamma rays (VHE, E > 100 GeV) led us to
the identification of extremely energetic processes and particle acceleration
sites both within our Galaxy and beyond. We expect that VHE facilities, like
CTA, will explore these sources with an unprecedented level of detail. However,
the transient and unpredictable nature of many important processes requires the
development of proper monitoring strategies, to observe them. With this study,
we estimate the properties of VHE transients that can be effectively detected
by monitoring facilities. We use data collected by the Fermi-LAT instrument,
during its monitoring campaign, to select events that are likely associated
with VHE emission. We use this sample to estimate the frequency, the luminosity
and the time-scales of different transients, focusing on blazar flares and
Gamma Ray Bursts (GRBs). We discuss how the balance between Field of View,
sensitivity and duty cycle of an observatory affects the likelihood to detect
transients that occur at the inferred rates and we conclude describing the
contribution that current and near-future monitoring facilities can bring to
the identification and study of VHE transient emission.
