I'm not sure whether this is technically feasible or not, but when using combination headphone/mic device attached to the playdate via TRRS plug, it would be awesome to support the available buttons via the PlaydateSDK: Volume Up, Volume Down, Play/Pause and a fourth button often used for voice control.
Looking at the Android 3.5mm Headset Specification it appears that each button applies a voltage change by passing the microphone signal through different resistors changing the impedance. Research suggests that Android and iOS had conflicting methods for communicating button these presses.
I'm not sure my devices work the same way as the buttons are supported by my apple devices (macbook, iphone via headphone adapter dongle) but I did find multiple mentions that the play/pause (answer/hangup) button was similar enough between the two standards that this button would often work for both android and iOS/macOS devices with headphones designed for the other. Before the introduction of the new headphones with volume control for the iPhone 3GS, I believe the original iPhone and iPhone 3G included headphones with a single play/pause button in the microphone.
Since detecting this change is an analog thing, I'm not sure whether the existing hardware in the Playdate can support this, nor whether it would be worth the effort or possible to add support to existing devices even if it were technically possible. My guess is that it might be possible to support the play/pause, but that the other buttons might require a different hardware design to support.
Who knows though. Just thought I'd mention it.