In the age of IoT and mobile platforms, ensuring that content stay authentic whilst avoiding overburdening limited hardware is a key problem. This study introduces hybrid Fast Wavelet Transform & Additive Quantization index Modulation (FWT-AQIM) scheme, a lightweight watermarking approach that secures digital pictures on low-power, memory-constrained small scale devices to achieve a balanced trade-off among robustness, imperceptibility, and computational efficiency. The method embeds watermark in the luminance component of YCbCr color space using low-frequency FWT sub-bands, minimizing perceptual distortion, using additive QIM for simplicity. Both the extraction and embedding processes run in less than 40 ms and require minimum RAM when tested on a Raspberry Pi 5. Quality assessments on standard and high-resolution images yield PSNR greater than equal to 34 dB and SSIM greater than equal to 0.97, while robustness verification includes various geometric and signal-processing attacks demonstrating near-zero bit error rates and NCC greater than equal to 0.998. Using a mosaic-based watermark, redundancy added enhancing robustness without reducing throughput, which peaks at 11 MP/s. These findings show that FWT-AQIM provides an efficient, scalable solution for real-time, secure watermarking in bandwidth- and power-constrained contexts, opening the way for dependable content protection in developing IoT and multimedia applications.