Gregory's Server
Nothing magical, look for the utilsplugin2, and then add an entry for Bing Streetside : "https://www.bing.com/maps?cp={#lat}~{#lon}&lvl=17&lvl=19.7&v=2&sV=1&style=x"
Every time you want to see available Bing Streetside imagery wherever is your location in JOSM, just activate utilsplugin (Shift+H key combo) and select that particular entry.