No, it's not quite like that.
"They are checking the beds" would be Wanakagua vitanda.
The present tense -na- indicates a present action, often (but not always) one that's underway.
The perfect tense -me- indicates a PAST action that has effects that are still current or relevant to the present. It contrasts with the simple past -li- which indicates a past action without implying that its effects continue to the present.
A lot of the time, these tenses translate directly into the equivalent English tenses.
ninapika = I am cooking / I cook
nimepika = I have cooked (ie. the food is ready)
nilipika = I cooked (eg. last night ... the food is not necessarily ready now and probably eaten long ago)
The major difference between Swahili and English with these tenses is that English uses a lot of adjectives that indicate a state whereas Swahili is more likely to use a verb that indicates entering into that state. For example, when we say in English "I'm drunk", the word "drunk" is an adjective that indicates my current state, which has been caused by my past action. Swahili effectively doesn't have a word that means exactly "drunk" but there is the verb kulewa which means "to get/become drunk". The way to say that you are drunk now is nimelewa, which literally means "I have gotten/become drunk" but because -me- specifically indicates that the results of the action are relevant now, it means that you're drunk now. There are lots of these kuchoka means "to become tired," and kuchelewa means "to become late". To say "I am tired" or "I am late" you use the perfect, nimechoka, nimechelewa, literally meaning "I have become tired/late" but essentially indicating your present state.
So, this sentence is not an example of this. In both languages, "checking" kukagua is an action just like cooking in the examples I gave above. Wamekagua means their checking is a past action that has results in the present ... the results would be that, for example, they know the state of the beds right now. (If you say walikagua ... they checked the beds, that might be, for example, last week, and the current state of the beds could be very different.) It doesn't mean they're in the process of checking, and, in fact, implies strongly that the checking is finished.
I hope that was clear! :-)