Many people have already created electric prototypes as already posted in the above links.
I think the biggest problem people face when building an electric trials bike is finding motors powerful enough and batteries light/small enough that can retain viable amounts of energy for prolonged riding periods.
Also, creating an electric trials bike nearer the size and weight of a push bike is unrealistic with current technology I've got to admit though, if you could create a trials push bike with a tiny motor linked to the back wheel and a small battery pack just to give you that extra 'power boost' when needed I'm sure it would be great fun and really push the boundaries of trials.