search / display / count
 filter
  stores
  > handle to/from differently for expense/income?
  expense/income
 group
  by category
  by time frame
   day
   week
   month
   quarter
   year
   custom?
  by store

sync
 simple protocol ("P" = hashes, "D: P" = data in P)
  A: tcp connect
  B: tcp accept
  A: PA
  B: D: PB \ PA
  B: PA \ PB
  A: D: PA \ PB
 works both centralized and decentralized

multiple categories?
 sum will be >100%
 sub-categories: same problem