At present, GNSS-IR sea surface height retrieval technology relies primarily on traditional geodetic GNSS receivers. However, due to their high cost and portability limitations, these devices struggle to meet the demands for low-cost and high-precision applications, which restricts the widespread adoption of this technology. To address this, our study utilizes smartphones for GNSS-IR sea surface height inversion experiments. By employing robust estimation techniques, we integrated multi-system and multi-frequency data to enhance the accuracy of the sea surface height inversion. The results indicate that the smartphone's overall retrieval accuracy is approximately 21 cm, with an average correlation coefficient of 0.96, performance comparable to that of traditional GNSS receivers. The multi-system multi-frequency data fusion further improved the sea surface height retrieval accuracy to 6.8 cm, with a correlation coefficient of 0.996. Compared to the initial retrieval results, this approach significantly enhanced both the temporal resolution and the accuracy of sea surface height retrieval. After smoothing, the accuracy of the fused retrieval results reached 6.1 cm. These findings demonstrate that smartphones can achieve centimeterlevel accuracy in sea surface height retrieval, making them a viable alternative to traditional GNSS receivers for GNSS-IR applications.