Computer tools for pronunciation annotation (IPA).
eSpeak
The most easy to use tool is eSpeak (and its fork eSpeak NG). It should be executed in the console:
> espeak -v la --ipa -q vocabulum
wɔkˈabʊlʊm
It works with many other languages too, and can be easily integrated into desktop dictionary lookup software (e.g. GoldenDict).
Classical Language Toolkit
Reconstruction of short and long vowels is a difficult task if they are not clearly distinguished in the printed text. In such situation, eSpeak often produces incorrect transcriptions (Latinus > [lˈatɪnʊs]). An attempt to solve this problem was made in the Classical Language Toolkit's module Macronizer, however it often fails too. CLTK is a programming library, not a ready to use software.