Alarms in rentals?

Was viewing an apartment today (looking to rent) which had no burglar alarm, and asked the letting agent about having one installed. He checked with the landlord and they say that if we rent the place, we can put in an alarm ourselves. I'm wondering if I should ask for the landlord to contribute if I do.

On the one hand, it would theoretically add to the value of his property a small amount and possibly deter damage from break-ins.

On the other hand, it's us that want the alarm, so the landlord might not be expected to pay anything (and he isn't obliged to, anyway).

Basically I'm asking: if I go ahead and foot the bill for an alarm on a rented property without contribution from the landlord, am I being had because I'm basically improving his property for free?

I've not signed a lease yet, and am waiting to find out the exact cost of an alarm before I do. I'd be interested in hearing what ye think.