Watch It !

 

Parshas Hashavua עקב --- וקשרתם אתם לאות על ידכם In   שו"ע הל' תפילין כ"ז:ד  it says not to have a חציצה between the תפילין and the גוף. The רמ"א adds that this Halacha applies only to the actual תפילין but for the רצועות there is no need to be concerned with חציצה.  The משנה ברורה ס"ק ט"ז quotes from the אחרונים to be מחמיר even on the רצועות במקום ששייך לקשירה Wearing hand watches became popular in the past 100 years or so. Most watches before that were pocket watches. The first one to deal with the שאלה of wearing a watch under  the רצועות was the Tchehbiner Rav Zt"l who is more מחמיר than the מ"ב and holds to refrain from wearing a watch under the  רצועות even though it is not near the קשר. Harav Ovadya Yosef zt"l writes that he personally spoke to the Tchehbiner Rav  who told him that if the watch is placed past the 7 כריכות there is no problem of wearing it under the רצועות.