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It is a basic grammar that「いる」is used to show the existence of something alive and 「ある」is to show the existence of inanimate object in terms of 存在表現.
However, I found some people use "工夫がいる" instead of "工夫がある". Is it an exception?
人に伝えるコトって工夫がいるんです！
細胞内の物質を積極的に移動させる工夫がいる。
You are confusing 「居{い}る」 ("to exist") and 「要{い}る」 ("to be necessary").
In both of your two sentences, the verb is 「要る」, so it is just a normal usage. 「工夫がいる」, therefore, means "(it) requires ingenuity".
For the pronunciation of these two いる's and a few other verbs that are spelled 「いる」 if written in kana, see here:
