The P‐alert seismic network, an on‐site low‐cost earthquake early warning system (EEWS) located in Taiwan, has proven useful in earthquake events since 2010. This dense network can produce detailed shakemaps and identify the direction of the source rupture in near‐real time. Based on real‐time acceleration signals and the proposed time‐dependent anisotropic attenuation relationship with peak ground acceleration (PGA), ShakingAlarm, a regional early warning system add‐on to the original P‐alert network, can immediately provide (1) an accurate predicted PGA, before the arrival of the observed PGA, that will give a consistent lead time for hazard assessment and emergency response, (2) a predicted shakemap (PSM) that will converge faster to the final reported shakemap than the regional EEWS, and (3) a shake contour area‐based magnitude estimation that is robust, even in the absence of a measured shake contour area such as in the case of an offshore earthquake. Taking the 2016 6.4 Meinong earthquake as an example, the 14th second PSM from ShakingAlarm converges on the final shakemap better than the regional EEWS from the Central Weather Bureau (CWB) in Taiwan. According to our tests, ShakingAlarm provides a warning using modified Mercalli intensity (MMI) V that is consistent with the results of another on‐site EEWS (Strategies and Tools for Real Time Earthquake Risk ReducTion [REAKT]). Further performance tests were conducted with another five inland earthquakes from 2013 to 2014. Compared with traditional regional EEWSs, ShakingAlarm can effectively identify possible damage regions and provide valuable early warning information (PSM, predicted PGA, and magnitude) for risk mitigation.