Direct imaging surveys have revealed a population of substellar companions with masses around the deuterium-burning limit and orbits often farther than 100 au. The origin of these long-period planetary-mass companions (PMCs) is not fully understood. Studies have shown that some PMCs likely harbor accretion disks, offering a unique opportunity to reveal the dominant formation route. We have been carrying out multi-wavelength observations of accreting PMCs with ground-based and space facilities. In this talk, I will summarize our previous programs and highlight ongoing surveys.