Design and Implementation of a Grid-Independent, Non-Destructive Assistive Telemetry Node for Transitory and Rental Space Accessibility

Conventional domestic entry notification frameworks rely predominantly on acoustic propagation, presenting an institutionalized accessibility barrier for the deaf and hard-of-hearing demographic. While localized visual or haptic retrofitting solutions exist for permanent installations, they remain highly impractical for transitory, short-term rental, or travel accommodations where structural and electrical grid modifications are legally or structurally prohibited. This paper presents a novel, grid-independent, non-destructive assistive telemetry node designed specifically for temporary or mobile spatial environments. Utilizing a RISC-V based ESP32-C3 microcontroller, the system circumvents local spatial constraints by routing hardware-interrupt-driven trigger events over an automated network captive portal directly to a secure cloud broker (Telegram Bot API). The alert payload is translated at the user's mobile endpoint into multi-modal haptic-visual feedback streams, ensuring unconstrained geographical tracking. The hardware layer is packaged inside a custom additive-manufactured Polyethylene Terephthalate Glycol (PETG) enclosure optimized for rugged field mobility and tool-free deployment. Electrical characterization yields an optimized deep-sleep quiescent current floor of 7.2µA sustained via an ultra-low-power low-dropout (LDO) linear regulator stage. Empirical evaluations across eighteen distinct evaluation iterations demonstrate an overall mean end-to-end network latency of 5.86 seconds and a 100% transmission success rate, translating to a mathematically validated operational battery deployment shelf-life exceeding 14 to 16 months on standard commercial alkaline cells. Qualitative field evaluations with an assistive user cohort verify that the multi-modal notification pipeline significantly enhances situational awareness and independent living capacity without technical onboarding friction.