Satellite communication plays a crucial role in supplementing blind areas and enhancing ubiquitous coverage, to meet the ubiquitous connectivity demands of the future 6G Internet of Things (IoT). As a vital means for integrated space-ground and the intelligent interconnectivity of everything in the future 6G system, Direct-to-Smartphone technology has emerged as a global development hotspot and got widespread attention. This paper analyzes various technical routes and numerous technological challenges of Direct-to-Smartphone technology, and innovatively proposes key technical solutions, such as air interface adapting to high-dynamics, spaceborne ultra-large array multi-beam antennas, on-demand scheduling of extremely narrow beams for random access (RA), and high-integration smartphone design. These solutions support to realize Direct-to-Smartphone technology to adapt the high-dynamic characteristic of Low Earth Orbit (LEO) satellites, provide all-area broadband service, satisfy high-performance and miniaturized. Finally, this paper outlines three potential development directions for Direct-to-Smartphone technology.