I've come in my pants accidentally a few times.
1) When I have been real excited, without touching it, whether or not I had it out, I've had a few minor spurts. Then, had to jerk it off, to get the rest out. This is the typical story of comming as soon as you open your zipper - usually it means that you already started.
2) I've come in a wierd spontaneous way a few times too.
Once, going down the log floom at an amusment park, as wierd as that sounds. Another two seperate ocasions cheering at a baseball game.
Once when I was 15 running the 200 yard dash. Another two times running up the 2 flights of stairs to answer the telephone before the answering machine got it. Once laying back on a friends couch one afternoon when I was really tired, as soon as a closed my eyes, I came, and jolted back up.
All of these were full on shooting cannon ejaculations, but there was nothing sexual attached to it.
3) After having sex/ playing around for an extended period, but not coming, I have gotten up, or gone to take a shower & a few minutes later, like a half a gallon of come just pours out. My dick was soft or semi in all these cases with phenomenon #3
It definietly didn't shoot, just poured out, but there were the contractions and the happy feeling.
No though, never been able to come just by focusing on it.
That sounds even wierder than any of that