The design of fully-passive UHF RFID tags preserving cost-effectiveness, yet supplying augmented capabilities, represents an ambitious and stimulating challenge, as such devices would pave the way to a large class of applications where identification, computation, automatic cognition, and wireless sensing are required. In this work, two solutions are proposed. The former, named RAMSES, is optimized for RFID-based sensing and relies on a novel approach exploiting a new-generation I2C-UHF RFID chip. RAMSES is able to write sensor data into the EPC and communicate up to 5 m of distance from a conventional UHF RFID Class-1 Generation-2 (Gen2) reader. The latter solution, named SPARTACUS, renounces part of this long operating range in exchange for additional computing capabilities enabling an increased interaction with RFID readers. SPARTACUS represents the first example in literature of RFID device embedding sensing/actuation functionalities, distributed computation, and fully bidirectional communication with the reader. Satisfactory operating range, sensing, computation, data storage, and cost-effectiveness are the main strengths making the proposed devices definitely suitable for a wide array of novel and unconventional RFID applications.